CHAPTER XXIII.

GENERAL ACCOUNT OF THE SKELETON IN MAMMALIA (CONTINUED).

THE SKULL AND APPENDICULAR SKELETON.

THE SKULL.

MONOTREMATA. In both genera the cranium is thin-walled, has a fairly large cavity, and is very smooth and rounded externally. The sutures between many of the bones early become obliterated in a manner comparable to that in birds, and the facial portion of the skull is much prolonged.

In _Echidna_ the face is drawn out into a gradually tapering rostrum, formed mainly by the premaxillae, maxillae and nasals. The zygomatic arch is very weak, and the palate extends very far back. The tympanic forms a slender ring. The mandible is extremely slight, with no ascending portion, and but slight traces of the coronoid process and angle. The hyoid has a wide basi-hyal and stout thyro-hyals, while the anterior cornua are slender, and include ossified epi-hyals and cerato-hyals.

In _Ornithorhynchus_ the zygomatic arch is much stouter than in _Echidna_. The face is produced into a wide beak, mainly supported by the premaxillae, between whose diverging anterior ends there is a dumb-bell-shaped bone. The maxillae are flattened below, and each bears a large horny tooth, which meets a corresponding structure borne on a surface near the middle of the mandible. The mandible is considerably stouter than in _Echidna_, but the angle and coronoid process are but little developed. The infra-orbital foramen and the inferior dental and mental foramina of the mandible are all very large.

MARSUPIALIA. The skulls of the various types of the Marsupials frequently bear a strong superficial resemblance to those of some of the different groups of placental mammals. Thus the skull of the Dasyuridae resembles that of the Carnivora, the resemblance being most marked between the skulls of _Thylacinus_ and the dog. The skull of _Notoryctes_ is strongly suggestive of that of an Insectivore, and that of other Marsupials such as the wombat, recalls equally the characteristic features of a Rodent's skull. But, however much they may differ from one another, the skulls of all Marsupials agree in the following respects. (1) The brain cavity, and especially the cerebral fossa, has a very small comparative size. (2) The nasals are always large, and the mesethmoid is extensively ossified, and terminated by a prominent vertical edge. (3) Processes from the jugal and frontal in living forms never meet and enclose the orbit, but the zygomatic arch is always complete. (4) The jugal always extends back to form part of the glenoid fossa. (5) The lachrymal canal opens either external to or upon the margin of the orbit, and the nasal processes of the premaxillae never quite reach the frontals. (6) The posterior part of the palate is commonly pierced by large oval vacuities. (7) The tympanic is small and never fused to the bones of the cranium. (8) The carotid canal perforates the basisphenoid and not the tympanic bulla. (9) The optic foramen and sphenoidal fissure are confluent. (10) In every case except _Tarsipes_ the angle of the mandible is more or less inflected.

The skull of the extinct _Thylacoleo_ differs from that of all other Marsupials in the fact that the postorbital bar is complete. The hyoid is constructed on much the same plan in all Marsupials. It consists of a small basi-hyal, a pair of broad cerato-hyals, and a pair of strong thyro-hyals. The epi-hyals and stylo-hyals are generally unossified.

EDENTATA. In Sloths (Bradypodidae) the sutures become early obliterated, the cranial portion of the skull is rather high, and the facial portion very short. The lachrymal is very small, and its canal opens outside the orbit. The zygomatic arch is incomplete, and the jugal (fig. 91, 5) is curiously forked, but in a manner differing in the two genera. The premaxillae are very small,--in _Bradypus_ quite vestigial. The mandible is well developed, the angle being specially marked in _Bradypus_. In _Choloepus_ the symphysial part is drawn out in a somewhat spout-like manner (fig. 91, 6). In both genera the thyro-hyals are ankylosed with the basi-hyal.

In _Megatherium_ the general appearance of the skull is distinctly sloth-like, but the facial portion is more elongated, partly owing to the development of a prenasal bone, and the zygomatic arch is complete. The mandible is very deep in the middle, and is drawn out into a long spout-like process in front.

Anteaters (Myrmecophagidae) have a much modified skull, and this is especially the case in the Great Anteater, _Myrmecophaga_. The skull is smooth and evenly-rounded, in these respects recalling that of _Echidna_, but it is longer and tapers much more gradually than in _Echidna_. The occipital condyles are remarkably large. The premaxillae are small, and the long rostrum is chiefly composed of the maxillae and nasals with the mesethmoid and vomer. The zygomatic arch is incomplete, and there is no trace of a separation between the orbit and the temporal fossa. The palate is much elongated, the pterygoids meeting in the middle line just like the palatines. The mandible is very long and slender, there being no definite coronoid process, and a short and slight symphysis. The hyoid arch is noticeable for the length of the anterior cornu.

In the Armadillos (Dasypodidae) the skull varies a good deal in shape, but the facial portion is always tapering and depressed. The zygomatic arch is complete. In _Dasypus_ and _Chlamydophorus_ the tympanic bulla is well ossified.

In the Glyptodontidae the skull is very short and deep; the zygomatic arch is complete, and has a long downwardly projecting maxillary process. The mandible is massive, and has a very high ascending portion.

In the Manidae the skull is smooth and rounded, the zygomatic arch is incomplete, and the orbit is inconspicuous. The palate is long and narrow, but the pterygoids do not take part in its formation. The mandible is slightly developed and has no angle or coronoid process.

In _Orycteropus_ the zygomatic arch is complete, and there is a small postorbital process to the frontal. The mandible is well-developed, having a coronoid process and definite ascending portion, and the hyoid is well ossified.

SIRENIA. The skull, and especially the brain case of all Sirenia, is remarkable for the general density of the component bones, which, though often very thick, are without air sinuses. It is noticeable also for the roughness of the bones, and the irregular manner in which they are united together.

The cranial cavity is decidedly small, the reduction being specially noticeable in the cerebral fossa, which is not much larger than the cerebellar fossa. The foramen magnum is large, and the dorsal surface of the cranium narrow. The zygomatic arch is very strongly developed, the squamosal (fig. 92, 4) being especially prominent, and being drawn out not only into the zygomatic process, but also into a large post-tympanic process which articulates with the exoccipital. At the side of the skull between the squamosal, supra-occipital and exoccipital, there is a wide vacuity in the cranial wall, partially filled up by the very large periotic, which is ankylosed to the tympanic, but is not united to any other bones of the skull. The foramen lacerum medium is confluent with the foramen lacerum anterius, and the two together form an enormous vacuity on the floor of the skull, bounded chiefly by the exoccipital, basi-occipital, alisphenoid and squamosal. The jugal (fig. 92, 8) is large and in _Manatus_ sends up a strong process, which nearly or quite meets the postorbital process of the frontal, completing the orbit. In the other Sirenia the orbit is completely confluent with the very large temporal fossa. The lachrymal in _Manatus_ is very small, but is larger in _Halicore_. The premaxillae (fig. 92, 9) are large, but smaller in _Manatus_ than in the other genera, in all of which they are curiously bent down in front. Their upper margin forms the anterior border of a very large aperture lying high on the roof of the skull and extending back for a considerable distance. This aperture is formed by the union of the two anterior nares. The nasals are quite vestigial or absent, and the narial aperture is bounded above by the frontals; in its floor are seen the slender vomer and large mesethmoid. The palate is long and narrow, and formed mainly by the maxillae; behind it there is a large irregular process formed by the union of the palatine, pterygoid, and pterygoid plate of the alisphenoid. The mandible is very massive and has a very high ascending portion, a rounded angle (fig. 92, 10), and a prominent coronoid process; the two rami are firmly ankylosed together. The hyoid consists principally of the broad flat basi-hyal; the anterior cornua are but slightly ossified, while the thyro-hyals are not ossified at all.

CETACEA. The skull in all Cetacea, especially in the Odontoceti, is a good deal modified from the ordinary mammalian type.

In the _ARCHAEOCETI_ this modification is less marked than in either of the other suborders. The nasals and premaxillae are a good deal larger than they are in living forms, and the anterior nares are placed further forward. The maxillae do not extend back over the frontals, and there is a well-marked sagittal crest.

In the _MYSTACOCETI_ the skull is always quite bilaterally symmetrical, and is not so much modified from the ordinary mammalian type as in the Odontoceti. The parietals are not, as in the Odontoceti, separated by a wide interparietal, but meet; they are, however, hidden under the very large supra-occipital. The nasals are developed to a certain extent, and the nares, though placed very far back and near the top of the head, terminate forwardly-directed narial passages. Turbinal bones are also developed to some extent; this fact, and the occurrence of a definite though small olfactory fossa constituting important distinctions from the Odontoceti. The maxillae are large, but do not extend back to cover the frontals as in the Odontoceti. The zygomatic process of the squamosal is very large. The mandibular rami are not compressed, but are rounded and arched outwards, and never meet in a long symphysis.

_ODONTOCETI._ The skull departs widely from the ordinary mammalian type. The following description will apply to any of the following genera of the Delphinidae, _Phocaena_, _Globicephalus_, _Lagenorhynchus_, _Delphinus_, _Tursiops_, _Prodelphinus_, _Sotalia_.

The upper surface of the skull is more or less asymmetrical. The cerebral cavity is high, short and broad; and formed mainly by the cerebral fossa, the olfactory fossa being entirely absent. The supra-occipital (fig. 93, 3) is very large, and forms much of the posterior part of the roof of the skull. It has the interparietal (fig. 93, 7) fused with it, and completely separates the two parietals. The frontal (fig. 93, 10) is large and laterally expanded, forming the roof of the orbit, but is almost completely covered by an extension of the maxillae. The zygomatic arch is very slender, and is mainly formed by a rod-like process from the jugal (fig. 93, 15), the zygomatic process of the squamosal being short and stout.

The nasal passages are peculiarly modified, instead of passing horizontally forwards above the roof of the mouth, they pass upwards and even somewhat backwards towards the top of the skull (fig. 93, 23). They are bounded laterally by two processes from the premaxillae, the left of which is shorter than the right. The nasal cavities are narrow and without turbinals and the nasals (fig. 93, 19) are almost as much reduced as in Sirenia.

In front of the nasal openings the face is prolonged as a narrow beak or rostrum of varying length, formed by the maxillae and premaxillae surrounding the vomer and large mesethmoid (fig. 93, 11), which sends forwards a long partially cartilaginous process, and is fused behind with the presphenoid (fig. 93, 8). The basi-occipital (fig. 93, 1) too is fused with the basisphenoid. The foramen rotundum is confluent with the sphenoidal fissure, and the foramen ovale with the foramen lacerum medium and the foramen lacerum posterius. The palate is mainly formed by the maxillae; the premaxillae and palatines (fig. 93, 17), though both meet in symphyses, forming very little of it. The pterygoids vary in size in the different genera, sometimes as in _Lagenorhynchus_ and _Delphinus_ meeting in the middle line, sometimes as in _Phocaena_ and _Globicephalus_ (fig. 93, 18) being widely separated. The tympanic and periotic are not fused together, and the periotic has generally no bony union with the rest of the skull. The mandible is rather slightly developed, with the rami straight, compressed and tapering to the anterior end. The condyle is not raised at all above the edge of the ramus; the angle is rounded and the coronoid process is very small. _Platanista_ has a curiously modified skull; the rostrum and mandible are exceedingly long and narrow, and arising from the maxillae are two great plates of bone which nearly meet above.

In the Physeteridae the skull is raised into a very prominent crest at the vertex behind the nares. In front of this in _Hyperoödon_ a pair of ridges occur, formed by outgrowths from the maxillae. In the old male these ridges reach an enormous size and almost meet in the middle line. In _Physeter_, the Sperm whale, these ridges are not developed; the maxillae and premaxillae unite with the other bones of the crest enclosing an enormous half basin-shaped cavity, at the base of which are the very asymmetrical anterior narial apertures.

In all living Cetacea the hyoid has the same general shape, consisting firstly of a crescentic bone formed by the fusion of the thyro-hyals with the basi-hyal, and secondly of the anterior cornu formed principally by the strong stylo-hyal.

UNGULATA. None of the distinctive characters separating the Ungulata from the other groups of mammals are drawn from the skull. But in the Ungulata vera as opposed to the Subungulata a distinguishing feature is found in the fact that the lachrymal and jugal form a considerable part of the side of the face, and that the jugal always forms the anterior part of the zygomatic arch, the maxillae taking no part in it.

UNGULATA VERA.

_ARTIODACTYLA._ The skull in Artiodactyla differs from that in Perissodactyla in the fact that the posterior end of the nasal is not expanded and there is no alisphenoid canal.

The skulls in the different groups of Artiodactyla differ considerably from one another.

The skull of the Pig[166] will be described as illustrative of the skull in the Suina. In the Pig as in most Artiodactyla the face is bent sharply down on the basicranial axis, the commencement of the vomer being situated below the mesethmoid instead of in front of it as in most skulls. The occipital region of the skull is small, and the line of junction of the supra-occipital and parietals is raised into a prominent occipital crest. The parietal completely fuses at an early stage with its fellow, and the exoccipital is drawn out into a long paroccipital process (fig. 94, A, 8). The frontal is large and broad and drawn out into a small postorbital process. The lachrymal too is large and takes a considerable part in forming the side of the face in front of the orbit, as does also the jugal, though to a less extent. The face is long and tapers much anteriorly. The nasals are long and narrow, as are the nasal processes of the premaxillae, which do not however reach the frontals. A prenasal ossicle is developed in front of the mesethmoid. The palate is long and narrow, the pterygoid (fig. 94, A, 10) is small, but the pterygoid process of the alisphenoid is prominent. The squamosal is small and has the tympanic fused with it; the tympanic is dilated below, forming a bulla (fig. 94, A, 9) filled with cancellous bone, and above forms the floor of a long upwardly-directed auditory meatus. The mandible has a high ascending portion and a small coronoid process (fig. 94, B, 13). The hyoid differs from that of most Ungulates, the stylo-hyal being very imperfectly ossified.

In _Hippopotamus_ the skull though essentially like that of the pig is much modified in detail. The brain cavity is very small, while the jaws are immensely developed. The face contracts in front of the orbits and then expands again greatly, to lodge the enormous incisor and canine teeth. The postorbital bar is complete or nearly so, and the orbits project curiously outwards and slightly upwards; the lachrymal is thin and much dilated. The squamosal is drawn out into a postglenoid process, and the hamular process of the pterygoid is prominent. The tympanic bulla is filled with cancellous bone. The mandible is enormously large, the symphysis is long, the angle much expanded and drawn out into a process which projects outwards and forwards.

Among extinct forms related to the Suina, _Cyclopidius_ is noticeable for having large vacuities in the lachrymo-nasal region, while _Cotylops_ has the postorbital bar complete; both these forms are from the North American Miocene.

In the Tylopoda and Tragulina the skull resembles in most respects that of the Ruminants, shortly to be described; but it is allied to that of the Suina in having the tympanic bulla filled with cancellous bone. The tympanic bulla is better developed in the Tragulina than in most Ungulates.

Among Ruminants, the Bovidae, that large group including the Oxen, Sheep, and Antelopes, as a rule have the face bent on the basicranial axis much as in the Suina. The parietals are generally small and early coalesce, the frontals are large and are usually drawn out into horn cores, which are however absent in the skulls of some domestic varieties of sheep and oxen, and also in some of the earlier extinct forms of Bovidae. These horn cores are formed internally of cancellous bone, and on them the true epidermal horns are borne. In young animals there is a distinct interparietal, but this early fuses with the supra-occipital, and in the oxen also with the parietals. The occipital crest is generally well marked, but in the genus _Bos_ becomes merged in a very prominent straight ridge running between the two horn cores; this ridge, which contains air cells communicating with those in the horn cores, is not nearly so well marked in _Bison_. There is often, as in _Gazella_, a vacuity on the side of the face between the nasal, frontal, lachrymal, and maxillae, but this is not found in oxen or sheep. The premaxillae are small, the nasals are long and pointed, and the turbinals are much developed. The Saiga antelope has a curiously specialised skull; the nasals are absent or have coalesced with the frontals and the anterior nares are enormously large. In all Ruminants the lachrymal is large and forms a considerable part of the side of the face; it often bears a considerable depression, the _suborbital_ or _lachrymal fossa_, well seen in most of the smaller antelopes. The postorbital bar is complete, and the orbit is prominent and nearly circular. The palatines and pterygoids are moderately large, and the pterygoids have a backwardly-projecting hamular process. The squamosal is small, but has a postglenoid process. The tympanic is not fused to the periotic and has a small bulla not filled with cancellous bone. There is a large paroccipital process to the exoccipital and the mandible has a long slender coronoid process.

In the Cervidae and Giraffidae the face is not bent down on the basicranial axis as it is in the Bovidae. The frontals are drawn out, not into permanent horn cores as in the Bovidae, but into short outgrowths, the pedicels, upon which in the Cervidae long antlers are annually developed. These _antlers_ are outgrowths of bone, and are covered during development by vascular integument, which dries up and peels off when growth is complete. Every year they are detached, by a process of absorption at the base, and shed. They may occur in both sexes, as in the Reindeer, but as a rule they are found only in the male. They are generally more or less branched, and are sometimes of enormous size and weight, as in the extinct _Cervus megaceros_. In young animals they are always simple, but become annually more and more complicated as the animal grows older.

In the Giraffe the frontals bear a small pair of bony cores, which are at first distinct, but subsequently become fused to the skull. In the allied _Sivatherium_, a very large form from the Indian Pliocene, the skull bears two pairs of bony outgrowths, a pair of short conical outgrowths above the orbits, and a pair of large expanded outgrowths on the occiput.

The opening of the lachrymal canal is commonly double and the lachrymal fossa is large in the Cervidae and the Giraffidae except _Sivatherium_. The vacuity between the frontal, lachrymal, maxillae, and nasal is specially large.

The hyoid of Ruminants is noticeable for the development of the anterior cornua, which include stout and short cerato-hyals and epi-hyals, long and strong stylo-hyals and large tympano-hyals which are more or less imbedded in the tympanics.

_PERISSODACTYLA._ In the skull of Perissodactyles an alisphenoid canal is found and the nasals are expanded behind. Among the living animals belonging to this group the skull least modified from the ordinary type is that in _Rhinoceros_. In this form the skull is considerably elongated, the facial portion being very large. The occipital region is elevated, but the cranial cavity is small, the boundary line between the occipital and parietal regions being drawn out into a prominent crest, which is occupied by air cells. There is no postorbital process to the frontal, and the orbit is completely confluent with the temporal fossa. The nasals are fused together and are very strongly developed, extending far forwards, sometimes considerably beyond the premaxillae. In some extinct species, such as _Elasmotherium_ and the Tichorhine Rhinoceros, _R. antiquitatis_, the mesethmoid is ossified as far forwards as the end of the nasals. The nasals are arched and bear one or two roughened surfaces to which the great nasal horns are attached. The premaxillae are very small and the pterygoids are slender. The palate is long, narrow, and deeply excavated behind. The postglenoid process of the squamosal is well developed, and generally longer than the paroccipital process of the exoccipital. The tympanic and periotic are both small and are fused together. The condyle of the mandible is very wide, the angle rounded, and the coronoid process moderately developed.

In the Titanotheriidae, a family of extinct Perissodactyla from the Miocene of North America, the occipital region is much elevated, as is also the fronto-nasal region, the nasals (perhaps only in the male) bearing a pair of blunt bony outgrowths. Between these two elevated regions the skull is much depressed. The cranial cavity is very small, the orbit confluent with the temporal fossa, and the zygomatic arch massive.

In _Tapirus_ the orbit and temporal fossa are confluent. The nasals are small, wide behind and pointed in front, and are supported by the mesethmoid; the anterior nares are exceedingly large and their lateral boundaries are entirely formed by the maxillae. The postglenoid and post-tympanic processes of the squamosal are large. The periotic is not fused to the squamosal or to the small tympanic. The mandible is large and has the angle much developed and somewhat inflected.

_Palaeotherium_, which lived in early Tertiary times, has a skull much like that of the Tapir, especially as regards the nasal bones.

In the Horse and its allies (Equidae) the facial portion of the skull is very large as compared with the cranial portion, the nasals and nasal cavities being specially large. In the living species of the genus _Equus_ there is no fossa between the maxillae and lachrymal, but it occurs in some extinct species. The lachrymal and jugal form a considerable part of the side of the face; and the orbit though small is complete and prominent. The postorbital bar is formed by a strong outgrowth from the frontal, which unites with a forward extension of the squamosal. The squamosal may extend forwards and form part of the wall of the orbit, a very unusual feature, as in most mammals the squamosal stops before the postorbital bar. The palate is narrow and excavated behind as in _Rhinoceros_; the palatines take very little part in its formation. The glenoid surface for the articulation of the mandible is very wide. The squamosal gives rise to small postglenoid and post-tympanic processes, and the exoccipital to a large paroccipital process. The tympanic and periotic are ankylosed together, but not to any other bones.

In the SUBUNGULATA, the lachrymal and jugal do not form any considerable part of the side of the face, and the maxillae commonly takes part in the formation of the zygomatic arch.

_TOXODONTIA._ The skull in the Toxodontia shows several Artiodactyloid features, while the manus and pes are of a more Perissodactyloid type. The Artiodactyloid features are (1) the absence of an alisphenoid canal, (2) the fact that the palate is not excavated behind, and that the palatines form a considerable part of it, and (3) the fusion of the tympanic to the squamosal and exoccipital, forming the floor of an upwardly directed auditory meatus. The frontal has a fairly well developed postorbital process, but the orbit is confluent with the temporal fossa. The premaxillae is well developed, as is the paroccipital process of the exoccipital, especially in _Typotherium_. The mandible has a rounded angle and a coronoid process of moderate size. In _Typotherium_ the ascending portion is very massive.

_CONDYLARTHRA._ As far as is known the skull of these generalised Ungulates is depressed, and is frequently marked by a strong sagittal crest. The cranial cavity is small, the cerebral fossa in _Phenacodus_ being exceptionally small. The orbit is completely confluent with the temporal fossa.

_HYRACOIDEA._ The skull of _Procavia_ resembles that of Perissodactyles more than that of any other Ungulates, but differs strongly in the comparatively small size of its facial portion. The posterior portion of the cranium is rather high, the occipital plane being nearly vertical. There is a small interparietal. The nasals are wide behind, and the zygomatic arch is strongly developed, its most anterior part being formed by the maxillae. The jugal and parietal give rise to postorbital processes which sometimes meet, but as a rule the orbit is confluent with the temporal fossa; it is very uncommon for the parietal to give rise to a postorbital process, and even in _Procavia_ the frontal often forms part of the process. The alisphenoid canal, and postglenoid and paroccipital processes are well developed. The tympanic bulla is large and the periotic and tympanic are fused together, but not as a rule to the squamosal. The ascending portion of the mandible is very high and broad, the angle rounded and the coronoid process moderate in size. The hyoid is singular, there is a large flat basi-hyal prolonged laterally into two broad flattened thyro-hyals. Articulating with its anterior end are two large triangular cerato-hyals, which are drawn out into two processes meeting in the middle line.

_AMBLYPODA._ In the Uintatheriidae (Dinocerata) the skull has a very remarkable character, being long and narrow and drawn out into three pairs of rounded protuberances, a small pair on the nasals, a larger pair on the maxillae in front of the orbits, and the largest pair on the parietals. The cranial cavity, and especially the cerebral fossa, is extraordinarily small. The orbit is not divided behind from the temporal fossa. The mandible has a prominent angle, and a long curved coronoid process; its symphysial portion bears a curious flattened outgrowth to protect the great upper canines.

In _Coryphodon_ the skull is of a more normal character, being without the conspicuous protuberances. The cranial cavity though very small is not so small as in _Uintatherium_.

_PROBOSCIDEA._ The character of the skull in the young elephant differs much from that in the old animal. In very young individuals the skull is of a normal character, and the cranial cavity is distinctly large in proportion to the bulk of the skull. But as the animal gets older, while its brain does not grow much, the size of its trunk and especially of its tusks increases greatly; and consequently the skull wall is required to be of very great superficial extent in order to afford space for the attachment of the muscles necessary for the support of these heavy weights. This increase in superficial extent is brought about without much increase in weight of bone by the development of an enormous number of air cells in nearly all the bones of the skull; sometimes, as in the case of the frontal, separating the inner wall of the bone from the outer, by as much as a foot. This development of air cells is accompanied by the obliteration of the sutures between the various bones. The most noticeable point with regard to the cranial cavity is the comparatively large size of the olfactory fossa. The supra-occipital (figs. 96 and 97, 9) is large--exceedingly large in the adult skull; the parietals (figs. 96 and 97, 2) are also very large. The frontals send out small postorbital processes, but these do not meet processes from the small jugal, which forms only the middle part of the slender zygomatic arch, the anterior part being formed by the maxillae. The lachrymal (fig. 96, 15) is small and lies almost entirely inside the orbit. The anterior narial aperture (fig. 97, 8) is wide and directed upwards, opening high on the anterior surface of the skull. It is bounded above by the short thick nasals and below by the premaxillae. The narial passage is freely open, maxillo-turbinals not being developed. The palatine is well developed, the pterygoid is small and early fuses with the pterygoid process of the alisphenoid. The tympanic is united with the periotic but not with the squamosal, and forms a large auditory bulla. There are no paroccipital or postglenoid processes. The exoccipital is not perforated by the condylar foramen,--a very exceptional condition.

The mandible has a high ascending portion, is rounded off below and has no angle. The symphysial portion is long, narrow, and spout-like, and the coronoid process is small. The thyro-hyals are ankylosed with the basi-hyal, which is connected with the large forked stylo-hyals by ligament only.

RODENTIA. The cranial cavity is depressed, elongated, and rather small, and the cerebral fossa lies entirely in front of the cerebellar fossa. The occipital plane is vertical or directed somewhat backwards, and the supra-occipital does not form much of the roof of the cranium. The paroccipital processes of the exoccipitals are generally of moderate size; in the Capybara (_Hydrochaerus_), however, they are very long, and are laterally compressed and directed forwards. The parietals are small, and often become completely fused together; there is sometimes a small interparietal. The frontals in most genera have no trace of a postorbital process; in Squirrels, Marmots and Hares, however, one occurs, but in no case does it meet a corresponding process from the zygomatic arch, so the orbit and temporal fossa are completely confluent. In Hares the postorbital process of the frontal is much flattened, and has an irregular margin. The temporal fossa is always small, and in _Lophiomys_ is arched over by plates arising respectively from the parietal and jugal; a secondary roof is thus partially developed in a manner unique among mammals, but carried to a great extent in many Chelonia. The nasal bones and cavities are large, attaining their maximum development in the Porcupines (fig. 98, 1). The premaxillae is always very large, and sends back a long process which meets the frontal. The vomer is occasionally found persisting in two separate halves, a feature recalling the arrangement in Sauropsids. In many Rodents there is an enormous vacuity at the base of the maxillary portion of the zygomatic arch. It is sometimes as large as the orbit, and attains its maximum development in the Capybara and other Hystricomorpha; in the Marmots, Beavers, and Squirrels (Sciuromorpha), and in the Hares it is undeveloped. In _Lagostomus_ the maxillae bears an upwardly directed plate of bone, shutting off from this vacuity a space which is the true infra-orbital foramen.

The zygomatic arch is always complete, and in many cases the jugal extends back to form part at least of the glenoid surface for articulation with the mandible. In _Coelogenys_ the jugal and maxillary portion of the zygomatic arch is greatly expanded and roughened, and the maxillary portion encloses a large cavity. The palate in Rodents is narrow, and the space between the incisor and molar teeth passes imperceptibly into the sides of the face. The anterior palatine foramina form long, rather narrow slits in this region. The bony palate between the grinding teeth is sometimes as in the Hares very short, sometimes as in the Capybara very long. The maxillae extends back beneath the orbit to unite with the squamosal. The pterygoid is always small, but sometimes has a well-marked hamular process which in _Hystrix_, _Lagostomus_, and some other genera unites with the tympanic bulla. The periotic is large, and fused with the tympanic, which forms a prominent bulla, and is generally drawn out into a tubular meatus. The bulla attains its maximum development in _Chinchilla_ and _Dipus_.

The mandible is narrow and rounded in front, the two halves meeting in a long symphysis. The angle is generally drawn out into a long backwardly-projecting process, which is often pointed and directed upwards. In the Hares the angle is rounded. The coronoid process is never large.

There are a number of points in which the skull of the Duplicidentata (Hares and Rabbits) differs from that of other Rodents. (_a_) The sutures between the basi-occipital and basisphenoid, and between the basisphenoid and presphenoid remain open throughout life. (_b_) Much of the maxillae forming the side of the face in front of the orbit is fenestrated. (_c_) The optic foramina are united to form a single hole, much as in birds. (_d_) The coronoid process is slightly differentiated from the ascending portion of the mandible. The first two of these points have been thought to indicate degradation of the hares and rabbits as compared with higher mammals.

CARNIVORA[167]. It is characteristic of the skull in Carnivora that the glenoid fossa is deep, and the postglenoid process (fig. 75, 23) well developed. The condyle of the mandible is much elongated transversely. The orbit and temporal fossa in the great majority of forms communicate freely, the postorbital bar being incomplete.

_CARNIVORA VERA._ The axis of the facial portion of the skull is a direct continuation of that of the cranial portion. The cranial cavity though rather depressed is large, and generally long, though in Cats it is comparatively short and wide. The occipital plane is nearly vertical, and the exoccipitals are developed into fairly prominent paroccipital processes. The interparietal is commonly distinct, and the parietals unite in a long sagittal suture, which is often developed into a crest. The nasals (fig. 73, 4) are well developed, especially in Cats, and the nasal processes of the premaxillae do not nearly reach the frontals. A considerable part of the palate is formed by the palatine, and the maxillary portion is pierced by rather long anterior palatine foramina. The pterygoid has a hamular process. The zygomatic arch is strong, especially in Cats. Postorbital processes are developed on the frontal (fig. 73, 10) and jugal, but never form a complete postorbital bar. A carotid canal is well seen in the Ursidae, and to a less extent in the Felidae; in the Canidae there is an alisphenoid canal (fig. 75, 21).

The auditory bulla differs a good deal in the different groups. In the Bears (Ursidae) it is not much inflated, and is most prominent along its inner border; it is not closely connected with the paroccipital process. In the Cats it is very prominent, and its cavity is almost divided by a septum into two parts, the inner of which contains the auditory ossicles. The paroccipital process is closely applied to the bulla. In the Dogs the bulla is intermediate in character between that of the Cats and that of the Bears; it is partially divided by a septum, and is moderately expanded.

The mandible is well developed with a prominent angle (fig. 72, 26), and a large coronoid process. The hyoid consists of a broad basi-hyal, a long many-jointed anterior cornu and short thyro-hyals (fig. 72, 33).

The skull in the _CREODONTA_ is in most respects allied to that of the Canidae, but presents some ursine affinities. The tympanic bulla is fairly prominent, but has no well-developed septum. The cranial cavity is very small and narrow, the zygomatic arch standing away from it. The temporal fossa is of great size.

In the _PINNIPEDIA_ the cranial cavity is large and rounded. The skull is much compressed in the interorbital region, and in correlation with this compression the ethmo-turbinals are little developed, while the maxillo-turbinals are large. The orbit is large, and the temporal fossa smaller than in the Carnivora vera. In the Walrus (_Trichechus_) the anterior part of the face is distorted by the development of the huge canines. The Otariidae have an alisphenoid canal. The tympanic bulla is small in _Otaria_, large in the Phocidae, and flattened in the Walrus. The hyoid is similar to that in Carnivora vera.

INSECTIVORA. The skull varies much in the different members of the order Insectivora, but the following points of agreement are found. The cranial cavity is of small size, and is never much elevated. The facial part of the skull is generally considerably elongated, and the nasals and premaxillae are well developed. The zygomatic arch is usually slender or incomplete, and the coronoid process and angle of the mandible are commonly prominent.

In some Insectivora, such as _Galeopithecus_, _Tupaia_, and _Macroscelides_, the skull shows a higher type of structure than is met with in most members of the order. In these genera the cranial cavity is comparatively large, and the occipital plane is nearly vertical. The zygomatic arch is fairly strong, and the frontal and jugal give rise to postorbital processes which nearly or quite (_Tupaia_) meet. The tympanic bulla is well developed, and produced into a tubular auditory meatus, this being specially well marked in _Macroscelides_.

In the other Insectivora the cranial cavity is of smaller comparative size, and the orbit and temporal fossa are completely confluent, often without any trace of a postorbital bar. The occipital plane commonly slopes forwards. In the Hedgehogs (Erinaceidae) and Centetidae the tympanic is very slightly developed, forming a small ring. The zygomatic arch of Hedgehogs and _Gymnura_ is very slender, the jugal being but little developed and the squamosal and maxillae meeting one another; in the Centetidae the jugal is absent and the arch is incomplete.

The Moles (Talpidae) have an elongated, depressed and rounded skull with a very slender zygomatic arch formed by the squamosal and maxillae. The nasals are fused together, and the mesethmoid is ossified very far forwards. In the Shrews (Soricidae) there is no zygomatic arch; the tympanic is ring-like, and the angle of the mandible is very prominent. The hyoid has a transversely extended basi-hyal, a long anterior cornu with three ossifications, and thyro-hyals which are sometimes fused to the basi-hyal.

CHIROPTERA. In the frugivorous Flying Foxes (Pteropidae) the skull is elongated, and the cranial cavity is large and arched, though considerably contracted in front. There are commonly strong sagittal and supra-orbital crests. The parietals take a great part in the formation of the walls of the cranial cavity, the supra-occipital and frontals being small. The frontal is drawn out into a long postorbital process, but the zygomatic arch, which is slender, and formed mainly by the squamosal and maxillae, gives rise to only a small postorbital process, so that the orbit and temporal fossa are confluent. There is no alisphenoid canal, and the tympanics are very slightly connected with the rest of the skull. The mandible has a large coronoid process, a rounded angle, and a transversely expanded condyle.

In Insectivorous Bats the skull is generally shorter and broader than in the Pteropidae. The cranial cavity is large and rounded, and has thin smooth walls. The zygomatic arch is slender, and postorbital processes are not generally well developed. The premaxillae is generally small, sometimes absent. The tympanics are ring-like and are not connected with the surrounding bones. The angle of the mandible is distinct. The hyoid in most respects resembles that of the Insectivora.

PRIMATES. The characters of the skull differ greatly in the two suborders of Primates, the Anthropoidea and the Lemuroidea.

In the _LEMUROIDEA_ the general relative proportions of the cranium and face are much as in most lower mammals, and the occipital plane forms nearly a right angle with the basicranial axis. The postorbital processes of the frontals are commonly continued as a pair of ridges crossing the roof of the cranium and meeting the occipital crest. Though the postorbital bar is complete, the orbit and temporal fossa communicate freely below it. The lachrymal canal opens outside the orbit, and the lachrymal forms a considerable part of the side of the face. The tympanic is developed into a large bulla. The hyoid apparatus much resembles that of the Dog.

In the _ANTHROPOIDEA_ the skull differs greatly from that in the Lemuroidea. The cranial portion of the skull is very large as compared with the facial portion, though the comparative development varies, some monkeys, such as the baboons (Cynocephali) having the facial portion relatively large. The comparative size of the jaws does not vary inversely with the general development of the animal, some of the Cercopithecidae having comparatively larger jaws than some of the Cebidae. The great size of the cranial part of the skull is mainly due to the immense development of the cerebral fossa, which commonly completely overlaps the olfactory fossa in front, and the cerebellar fossa behind. This development also has the effect of making the ethmoidal and occipital planes lie, not at right angles to the basicranial axis, but almost in the same straight line with it. This is, however, not always the case, as the Howling Monkey (_Mycetes_) and also some of the very highest monkeys, the Gibbons (_Hylobates_), have the occipital plane nearly vertical to the basicranial axis. In adult Man the basi-occipital, exoccipitals and supra-occipital coalesce, forming the so-called occipital bone; while the basisphenoid, presphenoid, alisphenoids, orbitosphenoids and pterygoids form the sphenoid bone. The roof of the skull is partly formed by the large supra-occipital and frontals, but mainly by the parietals (fig. 99, 1), which in Man are of enormous extent.

In Man and in most monkeys, at any rate when young (fig. 99, B), the roof of the skull is smooth and rounded, but in many forms, such as the Baboons, in the adult the supra-orbital and occipital ridges are much developed. In the Gorilla this is also the case with the sagittal crest (fig. 99, A, 2). The bones of the upper surface of the cranium interlock with wavy outlines. The nasals vary much in length, being much shorter in man than in most monkeys; they commonly become early fused together, as do also the frontals. The vomer is well developed, and the ethmo-turbinal always forms part of the boundary of the orbit. There are frequently, as in many Lemuroidea, a pair of more or less well-marked ridges, crossing the roof of the skull from the postorbital processes of the frontals to the occipital crest. The orbit is completely encircled by bone, and the alisphenoid assists the jugal and frontal in shutting it off from the temporal fossa, leaving however a communication between the two as the sphenomaxillary fissure. In most cases the frontals meet one another in the middle line between the mesethmoid and orbitosphenoid, but in Man, Simia, and some Cebidae this does not take place. In nearly all Cebidae the parietal and jugal meet one another, separating the frontal and alisphenoid on the skull wall; in Man and all Old World monkeys, on the other hand, the alisphenoid and frontal meet and separate the jugal and parietal. The premaxillae nearly always send back processes which meet the nasals. The palate is rather short and both the palatine and the premaxillae take a considerable part in its formation. The pterygoid plate of the alisphenoid is decidedly large, and there is no alisphenoid canal. There is never any great development either of the paroccipital process of the exoccipital, or of the postglenoid process of the squamosal. The periotic and tympanic are always fused together; in Cebidae they form a small bulla, but a bulla is not developed in any Old World forms. The periotic is large, especially the mastoid portion, which forms a distinct portion of the skull wall between the squamosal and exoccipital. In Man and still more in Old World monkeys, the external auditory meatus is drawn out into a definite tube, whose lower wall is formed by the tympanic; in the Cebidae the tympanic is ring-like. The perforation of the periotic by the carotid canal is always conspicuous.

The mandible is rather short and broad, and the angle formed by the meeting of the two rami is more obtuse than in most mammals. The coronoid process is fairly well developed, and the angle is more or less rounded. In most Primates the condyle is considerably widened, but this is not the case in Man. In _Mycetes_ the mandible is very large, its ascending portions being specially developed. The hyoid of Primates is remarkable for the large expanded basi-hyal, which is generally concave above and convex below. The anterior cornu is never well ossified, but the thyro-hyal is always strong. In _Mycetes_ the basi-hyal is enormously large, forming a somewhat globular thin-walled capsule.

AUDITORY OSSICLES.

There are in mammals four auditory ossicles forming a chain extending from the fenestra ovalis to the tympanic membrane. Three of these, the =malleus=, =incus= and =stapes=, are always distinct, while the fourth, the =lenticular=, is smaller than the others and is sometimes not distinct. The names are derived from human anatomy and indicate in the case of the first three a more or less fanciful resemblance respectively to a hammer, an anvil and a stirrup. The ossicles are homologous as a whole to the hyomandibular of fishes and to the columellar chain of Sauropsids and Amphibians. The malleus is homologous to the extra-columella of Crocodiles and the stapes to the columella. The =malleus= when typically developed consists of a rounded _head_ (fig. 100, 1) which bears a surface articulating with the incus, and a short _neck_ continued into a process, the _manubrium_ (fig. 100, 5), which comes into relation with the tympanic membrane. From the junction of the neck and manubrium two processes are given off, a _processus longus_ or _gracilis_ (fig. 100, 4), which in the embryo is continuous with Meckel's cartilage, and a _processus brevis_ (fig. 100, 6). The =incus= generally consists of a more or less anvil-shaped portion which articulates with the malleus, and of a process which is connected with the stapes by the small =lenticular=. The =stapes= is generally stirrup shaped, consisting of a basal portion from which arise two _crura_ separated by a space the canal through which a branch of the pharyngeal artery runs The lenticular is frequently cartilaginous and sometimes is not developed at all.

The above is the arrangement of the auditory ossicles met with in the higher Mammalia, but in the lower Mammalia the characters approach more nearly to those met with in Sauropsids.

In MONOTREMES the ossicles, though distinctly mammalian in character, show a very low type of development. The incus is articulated, or often fused, with an outgrowth from the head of the malleus. The stapes is very much like a reptilian columella, having a single crus with no perforation.

In MARSUPIALS the ossicles are of a low type, but not so low as the rest of the skeleton might have led one to expect, and all or almost all the points showing a low grade of development may be paralleled among the Monodelphia. The lowest Marsupials as regards the ossicles are the Peramelidae, whose ossicles are of a frail papery consistence. The Didelphyidae on the other hand have the most highly developed ossicles, the malleus much resembling that of many Insectivores, and the stapes having two definite crura separated by a canal.

In EDENTATES the character of the ossicles varies much. In Sloths the stapes approaches that of Sauropsids in its narrowness and the slight trace of a canal; this character is however still more marked in _Manis_, whose stapes is as Sauropsidan as that of Monotremes, and consists of a nearly circular basal plate bearing a column which does not show any sign of division into crura. The stapes of other Edentates, such as ant-eaters, aard varks, and most armadillos, is of a high type and has well-developed crura. _Priodon_ has a lower type of stapes than _Dasypus_ and _Tatusia_.

The ossicles of the SIRENIA differ widely from those of all other mammals in their great density and clumsy form.

In CETACEA the ossicles are solid, though not so solid as in Sirenia, and their details vary much. The malleus is always firmly fused to the tympanic by means of the processus longus, and the manubrium is very little if at all developed. The incus has the stapedial end greatly developed, and the stapes has very thick crura with hardly any canal. The ossicles of the Mystacoceti are apparently less specialised than are those of the Odontoceti.

The auditory ossicles of the UNGULATA do not present any characters common to all the members of the group.

Among Ruminants they are chiefly remarkable for the development of a broad lamellar expansion between the head and the processus longus of the malleus. In some cases the malleus of the foetus differs strikingly from that of the adult. Among Perissodactyla the Rhinoceros and Tapir have the malleus of a low type, recalling those of Marsupials; while in the Horse the head is well developed, and the malleus is of a higher type.

The ossicles of _Procavia_, which recall those of the Equidae, are chiefly remarkable for the small size of the body of the incus. In Elephants the ossicles are large and massive.

In the RODENTIA (fig. 100, C) the malleus is generally characterised by a very broad manubrium. In many genera such as _Bathyergus_, and most of the Hystricomorpha such as _Hystrix_, _Chinchilla_ and _Dasyprocta_, the malleus and incus are ankylosed together.

CARNIVORA. In Carnivora vera the most striking feature of the malleus is the occurrence of a broad lamellar expansion between the head and neck and the processus longus. This however does not occur in some Viverridae. In the Carnivora vera the incus and stapes are small as compared with the malleus, but in the Pinnipedia they are large. In the Pinnipedia the auditory ossicles have a very dense consistence, and except in the Otariidae are very large. The stapes frequently has no canal, or only a very small one.

In INSECTIVORA the characters of the auditory ossicles are very diverse. Many forms such as shrews, moles, hedgehogs, and the Centetidae have a low type of malleus resembling that of Edentates. _Chrysochloris_ has very extraordinary auditory ossicles. The head of the malleus is drawn out into a great club-shaped process, the incus is long and narrow, and differs much from the ordinary type.

In CHIROPTERA the ossicles and especially the malleus much resemble those of shrews. The stapes is always normal in character, never becoming at all columelliform.

PRIMATES. In Man and the Anthropoid Apes the malleus has a rounded head, a short neck, and the manubrium, a processus longus and a processus brevis. The incus consists of an anvil-shaped portion from which arises a long tapering process. The stapes has diverging crura and consequently a wide canal. The crura in other monkeys do not diverge so much as in man and anthropoid apes. The New World monkeys have no neck to the malleus.

THE STERNUM[168].

In MONOTREMES and most MARSUPIALS the sternum does not present any characters of special importance. The presternum is strongly keeled in _Notoryctes_.

The sternum in EDENTATES is very variable: in the Sloths it is very long, the mesosternum of _Choloepus_ having twelve segments. In the ant-eaters and armadillos the presternum is broad and sometimes as in _Priodon_ strongly keeled. In _Manis macrura_ the xiphisternum is drawn out into a pair of cartilaginous processes about nine inches long.

In the SIRENIA the sternum is simple and elongated, and of fairly equal width throughout, in the adult it shows no sign of segmentation. Its origin from the union of two lateral portions can be well seen in _Manatus_.

Two distinct types of sternum are met with in the CETACEA. In the Odontoceti the sternum consists of a broad presternum followed by three or four mesosternal segments, but with no xiphisternum. Indications of the original median fissure can be traced, and are very evident in _Hyperoödon_. In the Mystacoceti, on the other hand, the sternum consists simply of a broad flattened presternum which is sometimes more or less heart-shaped, sometimes cross-shaped. Only a single pair of ribs are united to it.

The sternum in UNGULATA is generally long and narrow and formed of six or generally seven segments. The presternum is as a rule small and compressed, often much keeled, especially in the horse and tapir. The segments of the mesosternum gradually widen as followed back and the xiphisternum is often terminated by a cartilaginous plate.

In the RODENTIA the sternum is long and narrow and generally has a large presternum, and a xiphisternum terminated by a broad cartilaginous plate.

In the CARNIVORA, too, the sternum (fig. 76) is long and narrow and formed of eight or nine pieces, all of nearly the same size. The xiphisternum generally ends in an expanded plate of cartilage.

In INSECTIVORA the sternum is well developed but variable. The presternum is commonly large and is sometimes as in the Hedgehog (_Erinaceus_) bilobed in front, sometimes as in the Shrew (_Sorex_) trilobed. It is especially large in the Mole (_Talpa_) and is expanded laterally and keeled below.

In the CHIROPTERA the presternum is strongly keeled and so is sometimes the mesosternum.

Among PRIMATES, in Man and the Anthropoid Apes the sternum is rather broad and flattened; the mesosternum consists of four segments which are commonly fused together and the xiphisternum is imperfectly ossified.

THE RIBS.

Free ribs are borne as a rule only by the thoracic vertebrae; ribs may be found in other regions, especially the cervical and sacral, but these are almost always ankylosed to the vertebrae. As a general rule the first thoracic rib joins the presternum, while the succeeding ones are attached between the several segments of the mesosternum. Some of the posterior ribs frequently do not reach the sternum; they may then be attached by fibrous tissue to the ribs in front, or may end freely (_floating ribs_). There are generally thirteen pairs of ribs, and in no case do they have uncinate processes.

In MONOTREMES (fig. 102, B) each rib is divided not into two but into three parts, an intermediate portion being interposed between the vertebral and sternal parts. The sternal ribs are well ossified, and some are very broad and flat. The intermediate portions are unossified, those of the anterior ribs are short and narrow, but they become longer and wider further back.

In MARSUPIALS there are almost always thirteen pairs of ribs, whose sternal portions are very imperfectly ossified. _Notoryctes_ has fourteen pairs of ribs, eight of which are floating: the first rib is very stout, and is abruptly bent on itself to join the sternum. It has no distinct sternal portion. All the other ribs are slender.

Of the EDENTATES the Sloths have very numerous ribs; twenty-four pairs occur in _Choloepus_, and half of these reach the sternum. In the Armadillos there are only ten or twelve pairs of ribs, but the sternal portions are very strongly ossified. The first rib is remarkably broad and flat, and is not divisible into vertebral and sternal portions.

In the SIRENIA there are a very large number of ribs noticeable for their great thickness and solidity, but not more than three are attached to the sternum.

CETACEA. In the Whalebone whales the ribs are remarkable for their very loose connection both with the vertebral column and with the sternum. The capitula are scarcely developed, and the attachment of the tubercula to the transverse processes is loose. The first rib is the only one connected with the sternum. In the Toothed whales the anterior ribs have capitula articulating with the centra, as well as tubercula articulating with the transverse processes; in the posterior ones, however, only the tubercula remain. Seven pairs of well-ossified sternal ribs generally meet the sternum. In the Physeteridae most of the ribs are connected to the vertebrae by both capitula and tubercula.

In the UNGULATA the ribs are generally broad and flattened, and this is especially the case in the genera _Bos_ and _Bubalus_ (fig. 101, 6). The anterior ribs are short and nearly straight, and sternal ribs are well developed. The Artiodactyla have twelve to fifteen pairs of ribs, the Perissodactyla eighteen or nineteen, and _Procavia_ twenty to twenty-two. The Elephant has nineteen to twenty-one pairs, seven of which may be floating ribs.

In the RODENTIA there are generally thirteen pairs of ribs, which do not present any marked peculiarities.

The CARNIVORA have thirteen to fifteen pairs of ribs, whose vertebral portions are slender, nearly straight and subcylindrical, while their sternal portions are long and imperfectly ossified (fig. 76, 5). There is nothing that calls for special remark about the ribs, in either INSECTIVORA or CHIROPTERA.

PRIMATES. In Man and the Orang (_Simia_) there are generally twelve pairs of ribs; in the Gorilla and Chimpanzee (_Anthropopithecus_), and Gibbons (_Hylobates_), there are thirteen, in the Cebidae twelve to fifteen, and in the Lemuroidea twelve to seventeen pairs. The first vertebral rib is shorter than the others, and the sternal ribs generally remain cartilaginous throughout life, though in man the first may ossify.

APPENDICULAR SKELETON.

THE PECTORAL GIRDLE.

By far the most primitive type of the pectoral or shoulder girdle is found in the MONOTREMATA. The scapula (fig. 102, A, 1) is long and recurved, and has only two surfaces, one corresponding to the prescapular[1] fossa, the other to the postscapular[1] and subscapular[169] fossae. The coracoid is a short bone attached above to the scapula and below to the presternum; it forms a large part of the glenoid cavity. In front of the coracoid there is a fairly large flattened epicoracoid (fig. 102, 6); there is also a large =T=-shaped interclavicle (fig. 102, 4), which is expanded behind and rests on the presternum. The clavicles rest on and are firmly united to the anterior border of the interclavicle. This shoulder girdle differs greatly from that of any other mammals, and recalls that of some Lacertilia.

In MARSUPIALS, as in all mammals except the Monotremes, the shoulder girdle is much reduced; there are no epicoracoids and interclavicle, and the coracoid forms simply a small process on the scapula, ossifying from a centre separate from that giving rise to the rest of the bone. The scapula has a long acromion, and a clavicle is always present except in _Perameles_. Unossified remains of the precoracoids are found at either end of the clavicle. The scapula of _Notoryctes_ has a very high overhanging spine, and there is a second strong ridge running along the proximal part of the glenoid border.

The shoulder girdle of the EDENTATA shows some very curious variations. In _Orycteropus_ the scapula is of very normal form and the clavicle is well developed. In the Pangolins and Anteaters the scapula is very broad and rounded; there is no clavicle in the Pangolins, and generally only a vestigial one in Anteaters. In Armadillos, Sloths, and Megatheriidae, the acromion is very long and the clavicle is well developed. In the Sloths, _Megatherium_, and _Myrmecophaga_, a connection is formed between the coracoid, which is unusually large, and the coracoid border of the scapula, converting the coraco-scapula notch into a foramen. In _Bradypus_ the clavicle is very small, and is attached to the coracoid, which sometimes forms a distinct bone[170].

In the SIRENIA the scapula is somewhat narrow and curved backwards: the spine, acromion, and coracoid process are moderately developed, and there is no clavicle.

CETACEA. In nearly all the Odontoceti the scapula is broad and somewhat fan-shaped; the prescapular fossa is much reduced, and the acromion and coracoid process form flattened processes, extending forwards nearly parallel to one another. Some of the Mystacoceti, such as _Balaenoptera_, have a broad, fan-shaped scapula, with a long acromion and coracoid process, extending parallel to one another. Others, such as _Balaena_, have a higher and narrower scapula, with a smaller coracoid process.

In UNGULATA the scapula is always high and rather narrow, and neither acromion nor coracoid process is ever much developed. In no adult Ungulate except _Typotherium_ is there any trace of a clavicle, but a vestigial clavicle has been described in early embryos of sheep[171].

UNGULATA VERA. In the Ruminantia the suprascapular region (fig. 103, 5) is very imperfectly ossified, and when this is removed the upper border of the scapula is very straight (fig. 101, 5). The spine is prominent, and generally has a fairly well-marked acromion. In _Hippopotamus_ the acromion is fairly prominent, but in the other Suina, though the spine is prominent, the acromion is not developed. The Perissodactyla have no acromion, but while the Equidae and _Hyracotherium_ have the scapula long and slender, with the spine very slightly developed, the other living Perissodactyla have the spine prominent and strongly bent back at about the middle of its length.

SUBUNGULATA. _Typotherium_ (Toxodontia) differs from all other known Ungulates in having well-developed clavicles; its scapula has a strong backwardly-projecting process, much like that in _Rhinoceros_.

_Phenacodus_ (Condylarthra), has a curiously rounded scapula, with the coracoid and suprascapular borders passing imperceptibly into one another. The scapula resembles that of a carnivore more than does that of any existing Ungulate.

_Procavia_ has a triangular scapula with a prominent spine and no acromion; there is a large unossified suprascapular region.

The scapula in the Proboscidea has a large rounded suprascapular border and a narrow, slightly concave glenoid border. The spine is large, and has a prominent process projecting backwards from about its middle. The spine lies towards the front end of the scapula, so that the postscapular fossa is much larger than the prescapular fossa.

In RODENTIA the shoulder girdle is of a rather primitive type. The scapula is generally high and narrow, somewhat as in Ruminantia; it differs, however, from the Ruminant scapula in having a high acromion, which is often, as in the Hares and Rabbits, terminated by a long metacromion. The development of the clavicle varies, and sometimes it is altogether absent. It is frequently connected by cartilaginous bands or ligaments (fig. 104, 7 and 9), on the one hand with the scapula, and on the other with the sternum. These unossified bands are remains of the precoracoid. Epicoracoidal vestiges of the sternal ends of the coracoids (fig. 104, 11) are also often present.

In the CARNIVORA VERA the scapula is large, and generally has rather rounded borders. The spine and acromion are well developed, and the prescapular and postscapular fossae are nearly equal in size. The coracoid is very small, and the clavicle is never completely developed, being often absent, as in the Bears and most of their allies. In the Seals (Phocidae) the scapula is elongated and curved backwards, and has a very concave glenoid border. In the Eared Seals (Otariidae) the scapula is proportionally much larger and wider, the prescapular fossa being specially large, and being traversed by a ridge, which converges to meet the spine.

In the INSECTIVORA the shoulder girdle is well developed and, as in Rodents, remains are met with of various parts not generally seen in mammals. In the Shrews the scapula is long and narrow, and has a well-marked spine, whose end bifurcates, forming the acromion and metacromion. The clavicle is long and slender, and is connected with the sternum and acromion by vestiges of the precoracoid. Considerable remains of the sternal end of the coracoid are also found. In _Potamogale_, however, there are no clavicles. In the Mole the shoulder girdle is greatly developed, and of very remarkable form. The scapula is high and very narrow, with the spine and acromion very little developed. The other shoulder girdle element is an irregular bone, which articulates with the humerus and presternum, and is connected by ligaments with the scapula. This bone appears to represent both the coracoid and the clavicle, being formed partly of cartilage bone, partly of membrane bone.

In the CHIROPTERA the scapula is large and oval, and has a moderately high spine and a large acromion. The coracoid process is well developed and is often forked. The clavicles are also well developed, and vestiges of the precoracoid and of the sternal end of the coracoid are often found.

In PRIMATES the clavicle and coracoid process are always well developed. In Man and the Gorilla the scapula has a long straight suprascapular border, a well-developed coracoid process and spine, and a large curved acromion. Vestiges of the precoracoid occur at each end of the clavicle. The shape of the scapula varies much in the lower Primates.

THE UPPER ARM AND FORE-ARM.

In the MONOTREMATA the humerus is short, very broad at each end and contracted in the middle. The radius and ulna are stout and of nearly equal size, while the ulna has a greatly expanded olecranon.

In the MARSUPIALIA the humerus is generally a strong bone, broad at the distal end and having well marked deltoid and supinator ridges, which are specially large in _Notoryctes_. An ent-epicondylar or supracondylar foramen (fig. 105, 5) is almost always present except in _Notoryctes_. The radius and ulna are always distinct and well developed, and a certain amount of rotation can take place between them. The ulna of _Notoryctes_ has an enormous hooked olecranon which causes the bone to be nearly twice as long as the radius.

EDENTATA. The Sloths have long slender arm bones; the humerus is nearly smooth and has a very large ent-epicondylar foramen in _Choloepus_, but not in _Bradypus_. The radius and ulna can be rotated on one another to a considerable extent. The humerus in all other Edentates is very strong and has the points for the attachment of muscles much developed, especially in the Armadillos and Megatheriidae. An ent-epicondylar foramen is found in all living forms. The radius and ulna are well developed, but are not capable of much rotation.

In the SIRENIA the humerus is well developed and of a normal character. It is expanded at each end and has a prominent internal condyle, a small olecranon fossa, and no ent-epicondylar foramen. In the Dugong and _Rhytina_ there is a bicipital groove and the tuberosities are distinct, but in the Manatee there is no bicipital groove, and the tuberosities coalesce. The radius and ulna are about equally developed and ankylosed together at both ends.

In the CETACEA the arm bones are very short and thick. The humerus has a globular head, and a distal end terminated by two equal flattened surfaces to which the radius and ulna are united. There is no bicipital groove, and the tuberosities coalesce. The radius and ulna are flat expanded bones fixed parallel to one another, but the ulna has a definite olecranon. Scarcely any movement can take place between them and the humerus, and in old animals the three bones are often ankylosed together.

In the UNGULATA VERA the humerus is stout and rather short. The great tuberosity is always large and often overhangs the bicipital groove, it is especially large in _Titanotherium_ (_Brontops_). There is never an ent-epicondylar foramen. The radius is always large at both ends, but the condition of the ulna is very variable. Sometimes, as in _Tapirus_, _Rhinoceros_, _Macrauchenia_, Suina and Tragulina, the ulna is well developed, and quite distinct from the radius; but in most forms, although complete, it is much reduced distally, and is fused to the radius. Sometimes, as in the Horse and Giraffe, it is reduced to the olecranon and to a very slender descending process which does not nearly reach the carpus. In the Tylopoda, though the ulna is complete and its distal end is often distinct, it has coalesced with the radius throughout its whole length; the olecranon is generally very large.

SUBUNGULATA. In the large Condylarthra the humerus has an ent-epicondylar foramen, and the radius and ulna are stout bones nearly equal in size.

In _Procavia_ the humerus is rather long, and has a very prominent greater tuberosity, and a large supra-trochlear fossa, but no ent-epicondylar foramen.

In the Proboscidea the humerus is marked by a greatly developed supinator ridge, and is very long, longer than the radius and ulna. The ulna has a remarkable development, having its distal end larger than that of the radius, it has also a larger articular surface for the humerus than has the radius.

In RODENTIA the humerus varies much in its development according to the animal's mode of life. In the Hares it is long and straight, with a small distal end, and a slight deltoid ridge. In the Beaver on the other hand the deltoid and supinator ridges are considerably developed. There is generally a large supra-trochlear fossa, but no ent-epicondylar foramen.

CARNIVORA. In the Carnivora vera the humerus has large tuberosities, a prominent deltoid ridge and a deep olecranon fossa. The shaft is generally curved, and an ent-epicondylar foramen is often found, though not in the Canidae, Hyaenidae, and Ursidae. The radius and ulna are never united. The radius (fig. 77, B) has a very similar development throughout its whole length, while the ulna has a large olecranon (fig. 77, C, 11) and a shaft tapering somewhat towards the distal end.

In the Pinnipedia the arm bones are very strongly developed. The humerus has a very prominent deltoid ridge, and the proximal end of the ulna and distal end of the radius are much expanded.

In the INSECTIVORA the arm bones are well developed, and the radius and ulna, though sometimes united, are generally distinct; as a rule there is an ent-epicondylar foramen, but this is absent in the Hedgehog. The Mole has an extraordinary humerus, very short and curved, and much flattened and expanded at both ends. It articulates both with the scapula and coraco-clavicle. The ulna has a greatly developed olecranon.

In the CHIROPTERA both humerus and radius are exceedingly long and slender; the ulna is reduced to little more than the proximal end and is fused to the radius. There is no ent-epicondylar foramen.

All PRIMATES have the power of pronation and supination of the fore-arm, by the rotation of the distal end of the radius round that of the ulna.

In Man and the Anthropoid Apes the humerus is long and straight, and has a globular head; neither of the tuberosities, nor the deltoid nor supinator ridges are much developed. The olecranon fossa is deep and there is no ent-epicondylar foramen. The radius is curved and has a narrow proximal, and expanded distal end, the ulna is straighter than the radius and has the distal end much smaller than the proximal; the olecranon is not much developed.

In the lower Primates, although the radius and ulna are always quite separate, the power of pronation and supination is not nearly so great as in the higher forms. In most of the Cebidae and Lemurs an ent-epicondylar foramen occurs.

THE MANUS.

The Manus is divisible into two parts, viz. the carpus or wrist, and the hand which is composed of the metacarpals and phalanges. The carpal bones are always modified from their primitive arrangement, sometimes more, sometimes less. One modification however is always found in mammals, viz. the union of carpalia, 4 and 5 to form the _unciform_ bone. Two sesamoid bones are commonly developed, one on each side of the carpus, the _pisiform_ or one on the ulnar side being much the larger and more constant: it has been suggested that these represent respectively vestiges of a prepollex and a post-minimus digit[172].

One or more of the five digits commonly present may be lost, and sometimes all are lost except the third. The terminal or ungual phalanges of the digits are commonly specially modified to support nails, claws, or hoofs. There are as a rule two small sesamoid bones developed on the ventral or flexor side of the metacarpo-phalangeal articulations, and sometimes similar bones occur on the dorsal or extensor side.

MONOTREMATA. In _Echidna_ the carpus is broad, the scaphoid and lunar are united and there is no centrale. The pisiform is large and several other sesamoid bones occur. Each of the five digits is terminated by a large ungual phalanx. In _Ornithorhynchus_ the manus is more slender, but the general arrangement is the same as in _Echidna_.

MARSUPIALIA. The carpus has no centrale and the lunar is generally small or absent. Five digits are almost always present. In _Choeropus_ however the only two functional digits are the second and third, which have very long closely apposed metacarpals; the fourth digit is vestigial, but has the normal number of phalanges, while the first and fifth are absent. The manus in _Notoryctes_ is extraordinarily modified, the scaphoid and all the distal carpalia are apparently fused, the first, second, and fifth digits are very small, the third and fourth, though having only one phalanx apiece, bear each an enormous claw. Lying on and obscuring the ventral surface of the manus is a large bone, probably a sesamoid.

Among the EDENTATA there is a great diversity in the structure of the manus, the centrale is however always wanting, and except in _Manis_ the scaphoid and lunar are distinct. In the Sloths the manus is very long, narrow, and curved, and terminated by two or three long hooked claws, borne by the second and third, or the second, third and fourth digits. The fifth digit is absent, and the fourth is represented only by a small metacarpal. In the Anteaters the third digit is greatly developed and bears a long hooked claw. In _Myrmecophaga_ all five digits are fairly well though irregularly developed, in _Cycloturus_ the first, fourth, and fifth, are vestigial. In the Armadillos the manus is broad, and has strongly developed ungual phalanges. The digits, though almost always five in number, vary much in their relative arrangement. In _Dasypus_ they are regular, but are remarkably irregular in Priodon. The pollex is absent in Glyptodonts and in _Megatherium._ In _Megatherium_ the fifth digit is clawless while the second, third, and fourth bear enormous claws. In the Manidae the scaphoid and lunar are united; five digits are present, the third and fourth being very large, and all being terminated by deeply cleft ungual phalanges. In _Orycteropus_ the pollex is absent, while the other digits are terminated by pointed ungual phalanges.

In SIRENIA the general structure of the manus is quite of the ordinary mammalian type. In _Manatus_ most of the bones of the carpus are distinct, but in _Halicore_ many, especially those of the distal row, have coalesced. The digits are always five in number and have the normal number of flattened phalanges.

In the CETACEA, on the other hand, the manus is much modified by the fact that the number of phalanges may be greatly increased above the normal number of three, thirteen or fourteen sometimes occurring in each digit. These are believed to be duplicated epiphyses. In the Mystacoceti the manus remains largely cartilaginous, in the Odontoceti it is better ossified, and the phalanges commonly have epiphyses at both ends. In _Physeter_ the carpal bones also have epiphyses. The carpus generally consists of six bones arranged in two rows of three each. Five digits are generally present, but sometimes as in _Balaenoptera musculus_, there are four, the third being suppressed. Their relative development varies much. The Sperm Whale which till recently was placed in the entrance hall of the Natural History Museum at South Kensington has one phalanx to the first digit, four to the second, five to the third, four to the fourth, and three to the fifth. Generally the manus is short and broad, but sometimes, as in _Globicephalus_, it is much elongated owing to the great development of the second and third digits.

UNGULATA[173]. The manus of the members of this great order is of very great classificatory and morphological importance. All the members agree in having the scaphoid and lunar distinct, and in almost every case the ends of the digits are either encased in hoofs or provided with broad flat nails. It is by means of characters derived from the manus and pes that the group is subdivided into the Ungulata vera and the Subungulata.

In the UNGULATA VERA the manus is never plantigrade, and there are not more than four digits, the pollex being almost always completely suppressed: in _Cotylops_ among extinct Artiodactyla however a vestigial pollex is found. The centrale is absent, and the magnum articulates freely with the scaphoid, and is separated from the cuneiform by the unciform and lunar. All the bones of the carpus interlock strongly, and the axis of the third digit passes through the magnum and between the scaphoid and lunar.

There is a very strong distinction between the manus of the suborders Artiodactyla and Perissodactyla. In the Artiodactyla the axis of the manus passes between the third and fourth digits, which are almost equally developed and, except in the Hippopotami and some extinct forms such as _Anoplotherium_, have their ungual phalanges flattened on their contiguous surfaces.

In all _ARTIODACTYLA_ the third and fourth digits are large, but a gradual reduction in the second and fifth can be well traced. Thus in the Suina the second and fifth digits, though smaller than the third and fourth, are well developed and all four metacarpals are distinct. In the Tragulina too all four metacarpals are developed, and in _Dorcatherium_ the third and fourth commonly remain distinct as in the Suina. In the other Artiodactyla however the third and fourth metacarpals are almost always united, though indications of their separate origin remain. In some Ruminantia, such as many Deer, the second and fifth digits are reduced to minute splint bones attached to the proximal end of the fused third and fourth metacarpals, and to small hoof-bearing phalanges, sometimes attached to splint-like distal vestiges of the metacarpals, sometimes altogether unconnected with any other skeletal structures. In some other Ruminants, such as the Sheep and Oxen, the only remnants of the second and fifth digits are nodules of bone supporting the hoofs, and in others, such as the Giraffe, _Anoplotherium commune_, some Antelopes and the Tylopoda, all traces of these digits have disappeared. The Camels differ from all living Ungulata vera in not having the distal phalanges completely encased in hoofs, and from all except the Hippopotami in placing a considerable amount of the manus on the ground in walking.

While the manus of the Artiodactyla is symmetrical about a line drawn between the third and fourth digits, that of the _PERISSODACTYLA_ is symmetrical about a line drawn through the middle of the third digit, which is larger than the others and has its ungual phalanx evenly rounded and symmetrical in itself. The most reduced manus in the whole of the mammalia is found in the Horse and its allies, in which the third digit, terminated by a very wide ungual phalanx, is the only one functional. Small splint bones representing the second and fourth metacarpals are attached to the upper part of the third metacarpal. In _Hipparion_[174] and other early horse-like animals the second and fourth digits, though very small and functionless, are complete and are terminated by small hoofs. In _Rhinoceros_ the second and fourth digits are equally developed and nearly as large as the third, and reach the ground in walking, a vestige of the fifth is also present. In the Tapir (fig. 106, A) and _Hyracotherium_ the fifth digit is fully developed but is scarcely functional. In _Titanotherium_ (_Brontops_) (fig. 106, B) it is nearly as well developed as any of the others, and there is little or no difference between the relative development of the third and fourth digits.

The Chalicotheriidae[175], though distinctly Perissodactyles in various respects such as their cervical vertebrae and teeth, differ not only from all other Perissodactyles, but from almost all other Ungulates, in the very abnormal character of their manus. For while the carpus and metacarpus are like those of ordinary Perissodactyles, the phalanges resemble those of Edentates, each second phalanx having a strongly developed trochlea, and each distal one being curved, pointed and deeply cleft at its termination (fig. 106, C).

The Macraucheniidae, while agreeing with Perissodactyles in having only three digits, with the limb symmetrical about a line drawn through the middle of the third, have a carpus which approaches closely to the subungulate condition, the magnum articulating regularly with the lunar, and only to a slight extent with the scaphoid.

In the SUBUNGULATA the manus sometimes has five functional digits, and a considerable part of it rests on the ground in walking. The bones of the carpus retain their primitive relation to one another, the magnum articulating with the lunar, but not with the scaphoid. This character does not however hold in the Toxodontia, for in most of the animals belonging to this group the magnum does articulate with the scaphoid. The corner of the scaphoid just reaches the magnum also in Amblypoda.

As far as is known the _TOXODONTIA_ generally have three, sometimes five digits to the manus, and the third is symmetrical in itself--a Perissodactyloid feature.

In _Phenacodus_ (fig. 107, B) (_CONDYLARTHRA_) all five digits are well developed, the pollex being the smallest. The carpal bones retain their primitive arrangement, the magnum articulating with the lunar and not with the scaphoid. There is no separate centrale.

In the _HYRACOIDEA_ (fig. 107, C) the manus is very similar to that in _Phenacodus_, but a centrale is present and the pollex is much reduced.

The manus of the _AMBLYPODA_, such as _Coryphodon_ (fig. 107, A) and _Uintatherium_, is short and broad, with five well developed digits and large carpal bones. The carpals however interlock to a slight extent, and the corner of the magnum reaches the scaphoid.

In the _PROBOSCIDEA_ the manus is very short and broad, with large somewhat cubical carpals which articulate by very flat surfaces and do not interlock at all. All five digits are present, and none of them are much reduced in size. The manus in Proboscidea and in _Coryphodon_ is subplantigrade.

In the Tillodontia the manus is plantigrade and has pointed ungual phalanges, in this respect approaching the Carnivora. It differs however from that of all living Carnivora in having the scaphoid and lunar distinct.

In RODENTIA the manus nearly always has five digits with the normal number of phalanges: the pollex may however be very small as in the Rabbit, or absent as sometimes in the Capybara. The scaphoid and lunar are generally united, and a centrale may be present or absent. In _Pedetes caffer_ the radial sesamoid is double and the distal bone bears a nail-like horny covering. In _Bathyergus_ the pisiform is double. It is upon these facts that the contention for the former existence of prehallux and post-minimus digits has partly been based.

In living CARNIVORA the scaphoid, lunar and centrale are always united, forming a single bone. All five digits are present, but as a rule in Carnivora vera the pollex is small, and in _Hyaena_ is represented only by a small metacarpal. Sometimes, as in Cats and Dogs, the manus is digitigrade, sometimes, as in Bears, plantigrade. The ungual phalanges are large and pointed, and in forms like the Cats, whose claws are retractile, they can be folded back into a deep hollow on the ulnar side of the middle phalanx; a small radial sesamoid is often present.

In Pinnipedia the manus is large and flat and the digits are terminated by ungual phalanges which are blunt (sea lions and walrus), or slightly curved and pointed (seals). The pollex is nearly or quite as long as the second digit, and as a rule the digits then successively diminish in size.

The Creodonta differ from living Carnivora in the fact that the scaphoid and lunar are usually separate.

In INSECTIVORA the scaphoid and lunar are sometimes united, sometimes separate, and a separate centrale is usually present. There are generally five digits, but sometimes the pollex is absent. In the Mole the manus is greatly developed and considerably modified. It is very wide, its breadth being increased by the great development of the radial sesamoid which is very large and sickle-shaped. The ungual phalanges are also large and are cleft at their extremities.

In the CHIROPTERA the manus is greatly modified for the purpose of flight. The pollex is short and is armed with a rather large curved claw, the other digits are enormously elongated, the elongation in the case of the Insectivorous bats being mainly due to the metacarpals, and in the Frugivorous bats to the phalanges. In the Frugivorous bats the second digit is clawed as well as the pollex, in other bats this claw is always absent, and so is often the ungual phalanx, the middle phalanx then tapering gradually to its termination.

In PRIMATES as a rule the manus is moderately short and wide. The carpus has the scaphoid and lunar distinct, and generally also the centrale; sometimes however, as in Man, the Gorilla, Chimpanzee, and some Lemurs, the centrale has apparently fused with the scaphoid. There are almost always five well-developed digits, but in the genera _Colobus_ and _Ateles_ the pollex is vestigial.

The magnum in man is the largest bone of the carpus. The pisiform also is well developed, but there is no radial sesamoid. In Man, the Gorilla, Chimpanzee, and Orang, the carpus articulates only with the radius, in most Primates it articulates also with the ulna. The third digit of the Aye-Aye (_Chiromys_) is remarkable for its extreme slenderness.

THE PELVIC GIRDLE.

The pelvic girdle in all mammals except the Sirenia and Cetacea consists of two halves, usually united with one another at the symphysis in the mid-ventral line, and connected near their upper ends, with the sacral vertebrae. Each half forms one of the _innominate_ bones, and includes at least three separate elements, a dorsal bone, the ilium, and two ventral bones, the ischium and pubis. Very often a fourth pelvic element, the acetabular or cotyloid bone, occurs.

In the MONOTREMATA the pelvis is short and broad, and the pubes and ischia meet in a long symphysis. The acetabulum is perforated in _Echidna_ as in birds, but not in _Ornithorhynchus_. A pair of elongated slender bones project forwards from the edge of the pubes near the symphysis; these are sesamoid bones formed by ossifications in the tendons of the external oblique abdominal muscles, and are generally called _marsupial bones_.

In the MARSUPIALIA the ilia are generally very simple, straight, and narrow, while the pubes and ischia are well developed and meet in a long symphysis. Marsupial bones are nearly always prominent, but are not developed in _Thylacinus_ or _Notoryctes_. The ischium often has a well-marked tuberosity and in Kangaroos the pubis bears a prominent pectineal process on its anterior border close to the acetabulum. The pelvis in _Notoryctes_ differs much from that in all other Marsupials, the ilium and ischium being ankylosed with six vertebrae in a manner comparable to that of many Edentates.

In the EDENTATA the pelvis is generally well developed, but the symphysis is very short. In the Sloths the pelvis is rather weak and slender, the obturator foramina are very large and the ischia do not meet in a symphysis. In the Megatheriidae the pelvis is exceedingly wide and massive, and is firmly ankylosed with a number of vertebrae. In the Armadillos, Glyptodonts, Anteaters, and Pangolins it is much developed and firmly united to the vertebral column by both the ilia and the ischia. In _Orycteropus_ however the ischium does not become united to the vertebral column, and the pubis generally has a strongly developed pectineal process.

In the SIRENIA the pelvis is quite vestigial. In the Dugong it consists on each side of two slender bones, one of which represents the ilium and the other the ischium and pubis; the two bones are placed end to end and are commonly fused together. The ilium is attached by ligament to the transverse process of one of the vertebrae. In the Manatee each half of the pelvis is represented by a triangular bone connected by ligaments with its fellow and with the vertebral column. In neither Manatee nor Dugong is there any trace of an acetabulum but one can be made out in _Halitherium_.

In the CETACEA the pelvis is even more vestigial than in the Sirenia, consisting simply of a pair of small straight bones which probably represent the ischia, and lie parallel to and below the vertebral column at the point where the development of chevron bones commences.

In UNGULATA VERA the pelvis is generally rather long and narrow. The ilium is flattened and expanded in front (fig. 103, 8), but becomes much narrower and more cylindrical before reaching the acetabulum. Both pubis and ischium contribute to the symphysis which is often very long. The ischia are large and have prominent tuberosities, especially in Artiodactyles. In most Ruminantia there is a deep depression, the supra-acetabular fossa above the acetabulum, but this is not found in the Suina or Tylopoda.

SUBUNGULATA. In _Procavia_ the pelvis is long and narrow, and bears resemblance to that in Artiodactyles.

The Proboscidea have a very large pelvis set nearly at right angles to the vertebral column; the ilium is very wide, having expanded iliac[1] and gluteal[1] surfaces, and a narrow sacral[176] surface. The pubes and ischia are rather small, but both meet their fellows in the symphysis. _Uintatherium_ (suborder Amblypoda) also has a large and vertically placed pelvis (fig. 108) with a much expanded ilium. The pelvis however differs from that of the Proboscidea in the fact that the ischia do not meet in a ventral symphysis.

In many RODENTIA the ilia have their gluteal, iliac, and sacral surfaces of nearly equal extent; in the Hares, however, the gluteal and iliac surfaces are confluent. The pubes and ischia are always well developed and sometimes, as in the Hares, the acetabular bone also. In these animals the pubis does not take part in the formation of the acetabulum, and the ischium bears on its outer side a well-marked ischial tuberosity.

In the CARNIVORA the pelvis is long and narrow. The iliac surfaces (fig. 78, A, 5) are very small and the sacral large; the crest or supra-iliac border is formed by the union of the sacral and gluteal surfaces. The symphysis is long and includes part of both pubis and ischium. The ischial tuberosity (fig. 78, A, 10) is often well marked, and sometimes as in _Viverra_ the acetabular bone is distinct. In the Pinnipedia the pelvic symphysis is little developed, or sometimes not developed at all, and the obturator foramina are remarkably large.

In some INSECTIVORA such as _Galeopithecus_, there is a long pelvic symphysis, in others such as _Erinaceus_ and _Centetes_, it is very short, in others again such as _Talpa_ and _Sorex_, there is no pelvic symphysis. The acetabular bone is exceptionally large in _Talpa_ and _Sorex_.

In CHIROPTERA the pelvis is small and narrow, and in the great majority of cases the two halves do not meet in a ventral symphysis. The pubis has a strongly developed pectineal process, which occasionally unites with a process from the ilium enclosing a large pre-acetabular foramen.

PRIMATES. In Man and the Anthropoid Apes the pelvis is very large and wide, and the ilium has much expanded iliac and gluteal surfaces. The symphysis is rather short and formed by the pubis alone. The acetabulum is deep and the obturator foramen large, and there is frequently a well-marked ischial tuberosity. In the lower Anthropoidea the ilium is long and narrow and has a small iliac surface. The ischial tuberosities are large in the old world monkeys.

THE THIGH AND SHIN.

In the MONOTREMATA the femur is short, rather narrow in the middle, and expanded at each end. The great and lesser trochanters are large and about equally developed, but there is no third trochanter. The fibula is very large and is expanded at its proximal end, forming a flattened plate much resembling an olecranon. The patella is well developed.

In the MARSUPIALIA there is no third trochanter to the femur, the fibula is well developed but not the patella as a general rule. _Notoryctes_ has a femur with a prominent ridge extending some little way down the shaft from the great trochanter; the tibia has a remarkably developed crest, and the fibula has its proximal end much expanded and perforated; there is an irregularly shaped patella closely connected with the proximal end of the tibia.

EDENTATA. In the Sloths the leg bones are all long and slender. The femur has no third trochanter, and the fibula is complete and nearly equal in size to the tibia. In the Megatheriidae the leg bones are extraordinarily massive, the circumference of the shaft of the femur in _Megatherium_ equalling or exceeding the length of the bone. There is no third trochanter in _Megatherium_. In most of the remaining Edentata the leg bones are strongly developed. The femur in the Armadillos and Aard Varks has a strong third trochanter, and the tibia and fibula are both large and are commonly ankylosed together at either end. The limb bones are very massive also in the Glyptodonts.

SIRENIA. In no living Sirenian is there any trace of a hind limb, but in _Halitherium_ a vestigial femur is found, which articulates with the pelvis by a definite acetabulum.

In the Mystacoceti among the CETACEA small nodules of bone or cartilage occur connected with the vestigial pelvis, and may represent the femur and tibia. No trace of the skeleton of the hind limb is known in the Odontoceti.

In the UNGULATA VERA the femur is noticeable for the size of the great trochanter (fig. 109, 2); there is no definitely constricted neck separating the head from the rest of the bone, and the lesser trochanter (fig. 109, 3) is not very prominent. All Perissodactyles except the Chalicotheriidae show a strongly marked third trochanter, but this is absent in all known Artiodactyles. The development of the fibula in general corresponds to that of the ulna. In _Rhinoceros_, _Macrauchenia_, _Tapirus_ and the Suina it is distinct and fairly well developed; in the Tragulina on the other hand it is vestigial, being reduced to the proximal end only. In the Ruminantia and Tylopoda also, it is much reduced forming merely a small bone attached to the distal end of the tibia, sometimes, as in the Red deer a slender vestige of the proximal end also is preserved quite detached from the distal portion; in the Horse this proximal portion is all that there is found of the fibula. The progressive diminution of the fibula can be well seen in the series of forms that are regarded as the ancestors of the Horse. The patella of the Ungulata vera is well ossified, but fabellae[177] are not usually found.

SUBUNGULATA. Of the Toxodontia, _Toxodon_ has no third trochanter while _Typotherium_ and _Astrapotherium_ have one. In the Condylarthra the femur has well-marked lesser and third trochanters, and the fibula and patella are well developed. In the Hyracoidea there is a slight ridge on the femur in the place of the third trochanter, the fibula is complete, but is generally fused to the tibia at its proximal end.

Of the Amblypoda, _Coryphodon_ has a third trochanter, but _Uintatherium_ has none; in this respect, in the vertical position and general appearance (fig. 108) of the limb, and in the articulation of the fibula with the calcaneum, the leg of _Uintatherium_ closely approaches that of the Proboscidea.

In the Proboscidea the femur is very long and straight, the development of trochanters is slight, and the fibula though slender is complete and articulates with the calcaneum.

A third trochanter is found in the Tillodontia.

In RODENTIA the femur is variable, the great trochanter is generally large and so sometimes is the third as in the Hares. In most Rodents as in the Beaver the fibula is distinct, sometimes as in the Hares it is united distally with the tibia. The patella is well developed, and so too are the fabellae as a general rule.

CARNIVORA. In the Carnivora vera the femur (fig. 79, A) is generally rather straight and slender, and has a very distinct head. The fibula (fig. 79, C) is always distinct and there is generally a considerable interval between it and the tibia. Fabellae (fig. 79, 7) are commonly present.

In the Pinnipedia the femur is short, broad and flattened, having a prominent great trochanter. The fibula is nearly as large as the tibia, and the two bones are generally ankylosed together at their proximal ends.

The Creodonta differ from all living Carnivores in having a femur with a third trochanter.

In the INSECTIVORA a third trochanter is sometimes developed. The fibula is sometimes distinct, sometimes fused distally with the tibia, thus differing from that of a Carnivore.

In CHIROPTERA the femur is straight, slender and rather short, with a small but well-developed head. The fibula may be well developed or quite vestigial or absent. Owing to the connection of the hind limb with the wing membrane the knee joint is directed backwards.

In PRIMATES the femur is rather long and slender, having a nearly spherical head and large great trochanter. The tibia and fibula are always distinct and well developed. Fabellae are not found in the highest forms but are generally present in the others.

THE PES.

The skeleton of the pes is in most respects a counterpart of that of the manus. Just as in the manus if one digit is absent it is the pollex, so in the pes it is the hallux. But while in the manus the third digit is always well developed, however much the limb may be modified, in the pes any of the digits may be lost. In all mammals the tibiale and intermedium fuse to form the _astragalus_, and the fourth and fifth tarsalia to form the _cuboid_. Sesamoid bones are considerably developed. In almost every case the phalanges and first metatarsal have epiphyses only on their proximal ends, while the remaining four metatarsals have epiphyses only on their distal ends.

In the MONOTREMATA all the usual tarsal bones are distinct, and the five digits have the normal number of phalanges. Several sesamoid bones are developed, the most important one, found only in the male, being articulated to the tibia and bearing the curious horny spur. The ungual phalanges of the pes like those of the manus, are deeply cleft at their extremities. In the Echidnidae the pes is turned outwards and backwards in walking.

In the MARSUPIALIA the pes is subject to great modifications, but in every case the seven usual tarsal bones are distinct. In the Didelphyidae the foot is broad, all five digits are well developed, and the hallux is opposable to the others. In the Dasyuridae the foot is narrow, and the hallux may be very small, or as in _Thylacinus_ completely absent. In _Notoryctes_ the pes is much less abnormal than the manus, and all five digits have the usual number of phalanges. The fifth metatarsal has a curious projecting process, and there is a large sesamoid above the hallux. In the Wombats (Phascolomyidae) the foot is short and broad, the digits are all distinct, and the hallux is divaricated from the others.

In the remaining marsupials the second and third metacarpals and digits are very slender, and are enclosed within a common integument. This condition is known as _syndactylism_, and its effect is to produce the appearance of one toe with two claws. In the Kangaroos (Macropodidae) the pes is very long and narrow, owing to the elongation of the metacarpals. The fourth digit is greatly developed, the fifth moderately so, while the hallux is absent, and the second and third digits are very small. The Peramelidae have the foot constructed on the same plan as in the Kangaroos, and in one genus _Choeropus_ the same type of foot is carried to a greater extreme than even in the Kangaroos. Thus the fourth digit is enormously developed, the second and third are small, and the fifth smaller still, while the hallux is absent. In the Phalangers and Koalas though the second and third toes are very slender, the hallux is well developed and opposable.

EDENTATA. In the Sloths the pes much resembles the manus, being long and narrow, but in both genera the second, third and fourth digits are well developed. Most of the other Edentates have a but little modified pes with the normal number of tarsal bones and the complete series of digits. In _Cycloturus_ however the hallux is vestigial and it is absent in Glyptodonts. _Megatherium_ has a greatly modified pes, the hallux is absent, and the second digit vestigial, while the third is very large, having an enormous ungual phalanx. The calcaneum too is abnormally large.

No trace of the pes occurs in either SIRENIA or CETACEA.

In the UNGULATA the pes like the manus is subject to much variation and is of great morphological importance.

In the UNGULATA VERA the pes is never plantigrade and never has more than four digits, the hallux being absent. The cuboid always articulates with the astragalus, and the tarsal bones strongly interlock. As was the case also with the manus, the pes is formed on two well-marked types characteristic respectively of the Artiodactyla and Perissodactyla.

_ARTIODACTYLA._ Just as in the manus, the third and fourth digits are well and subequally developed; their ungual phalanges have the contiguous sides flat, and the axis of the limb passes between them, and between the cuboid and navicular. The astragalus has both the proximal and distal surfaces pulley-like, and articulates with the navicular and cuboid by two facets of nearly equal size. The calcaneum articulates with the lower end of the fibula if that bone is fully developed.

In the Suina four toes are developed, and though in the Peccaries the third and fourth metatarsals are united, they are all distinct in most members of the group, as are all the tarsal bones. In the Hippopotami the four digits are of approximately equal size, and the middle ones do not have the contiguous faces of their ungual phalanges flattened.

In the Tragulina the cuboid, navicular, and two outer cuneiforms are united forming a single bone; all four metatarsals are complete and the two middle ones are united. In the Tylopoda and _Anoplotherium commune_ only the third and fourth digits are developed, their metatarsals are free distally, but are elsewhere united. In the Ruminantia the cuboid and navicular are always united and so are the second and third cuneiforms, while in _Cervulus_ all four bones are united together. The third and fourth metatarsals in Ruminants are always united in the same way as are the third and fourth metacarpals, while the second and fifth are always wanting. In Deer the second and fifth digits are usually each represented by three small phalanges, but in the Giraffe and most Bovidae the bones of these digits are wanting.

In the _PERISSODACTYLA_ the pes like the manus is symmetrical about a line drawn through the third digit; this line when continued passes through the external cuneiform, navicular and astragalus. The astragalus has its distal portion abruptly truncated, and the facet by which it articulates with the cuboid is much smaller than that by which it articulates with the navicular. The calcaneum does not articulate with the fibula. The tarsus in _Macrauchenia_ like the carpus differs from that of other Perissodactyles and resembles that of Subungulates in having the bones arranged in lines with little or no interlocking. The calcaneum resembles that of Artiodactyles in having a small facet for articulation with the fibula. _Tapirus_ (fig. 110, A), _Rhinoceros_ (fig. 110, B) and _Titanotherium_ have a short and broad foot with the usual tarsal bones and three well-developed digits,--a number never exceeded by any Perissodactyle. From this tridactylate limb a series of stages is exhibited by various extinct forms leading gradually to the condition met with in the Horse (fig. 110, D) in which the third toe is greatly developed, while the second and fourth are reduced to slender metatarsals attached to the proximal half of the third metatarsal.

In _Chalicotherium_ and _Agriochoerus_ the pes has the same abnormal characters as the manus, the digits being clawed and the ungual phalanges in _Chalicotherium_ deeply cleft.

In the SUBUNGULATA the pes is sometimes plantigrade and pentedactylate, the cuboid sometimes does not articulate with the astragalus, and the tarsal bones sometimes do not interlock.

In _Typotherium_ (_TOXODONTIA_) the hallux is absent and the other four digits are well developed; in _Toxodon_ and _Nesodon_ the pes is tridactylate. The tarsal bones have the regular Subungulate arrangement, the cuboid not articulating with the astragalus. The calcaneum articulates with the fibula as in Artiodactyles. The astragalus in most forms, but not in _Astrapotherium_, resembles that of the Ungulata vera in having a grooved proximal surface.

In _Phenacodus_ (_CONDYLARTHRA_) the tarsus is very little modified, five digits are present, the first and fifth being small and not reaching the ground.

In _Procavia_ only the three middle digits are present with a vestige of the fifth metacarpal.

In the _AMBLYPODA_ the pes (fig. 108) is very short and broad, all five digits are functional, and at any rate in _Coryphodon_ plantigrade, the hallux being the smallest. The astragalus is very flat, and the tarsals interlock to a slight extent, the cuboid articulating with both calcaneum and astragalus.

The pes in the _PROBOSCIDEA_ much resembles that in the Amblypoda, but differs in that the astragalus does not articulate with the cuboid, the tarsals not interlocking at all.

In the RODENTIA the structure of the foot is very variable. In Beavers the foot is very large, all five digits being well developed; the fifth metatarsal articulates with the outer side of the fourth metatarsal, and not with the cuboid, and there is a large sesamoid bone on the tibial side of the tarsus. In the Rats, Porcupines and Squirrels, there are five digits, in the Hares only four, and in the Capybara and some of its allies only three. In the Jerboa (_Dipus_) a curious condition of the pes is met with, as it consists of three very long metatarsals fused together and bearing three short toes, each formed of three phalanges. _Lophiomys_ differs from all other Rodents in having the hallux opposable.

CARNIVORA. In the Carnivora vera the pes is regular and shows little deviation from the normal condition. All the usual tarsal bones are present, but sometimes as in the Dogs, Cats, and Hyaenas, the hallux is vestigial. Sometimes as in the Bears the pes is plantigrade, sometimes as in the Cats and Dogs it is digitigrade. In this respect and in the character of the ungual phalanges, the pes closely corresponds with the manus. In the Sea Otter (_Latax_) the foot is large and flattened and approaches in character that of the Pinnipedia.

In the Pinnipedia the pes differs much from that in the Carnivora vera. In the Seals in which the foot cannot be used for walking, and is habitually directed backwards, the first and fifth digits are much longer and stouter than any of the others. In the Sea Lions which can use the pes for walking, the digits are all of nearly the same length, and in the Walrus the fifth is somewhat the longest.

In the INSECTIVORA the pes is almost always normal, and provided with five digits.

In the CHIROPTERA the pes is pentedactylate, and the digits are terminated by long curved ungual phalanges. In some genera the toes have only two phalanges. The calcaneum is sometimes produced into a long slender process which helps to support the membrane between the leg and the tail.

Among the PRIMATES Man has the simplest form of pes. In Man all five digits are well developed, the hallux being considerably the largest. Sesamoid bones occur only under the metatarso-phalangeal joint of the hallux.

In the other Primates the internal cuneiform has a saddle-shaped articulating surface for the hallux, which is obliquely directed to the side of the foot and opposable to the other digits. Two sesamoid bones are usually developed below each metatarso-phalangeal joint, and one below the cuboid. The second digit in Lemurs, and all except the hallux in _Chiromys_ have pointed ungual phalanges; in all other cases the ungual phalanges are flat. In some of the Lemuroidea, especially _Tarsius_, the tarsus is curiously modified by the elongation of the calcaneum and navicular.

FOOTNOTES:

[165] The figure was drawn from a photograph and the size of the jaws relatively to the cranium is exaggerated.

[166] See W.K. Parker, "On the Structure and Development of the Skull in the Pig." _Phil. Trans._ pp. 289-336, 1874.

[167] See W.H. Flower, "On the value of the characters of the base of the cranium in the classification of the order Carnivora." _P.Z.S._ 1869, p. 5.

[168] See W.K. Parker, _Monograph of the shoulder-girdle and sternum of the Vertebrata_, _Ray Soc._ 1868.

[169] See p. 405.

[170] See E. Lydekker, _P.Z.S._ 1895, p. 172.

[171] See H. Wincza, _Morph. Jahr._ XVI. p. 647, 1890.

[172] See K. Bardeleben, _P.Z.S._, 1889, p. 259.

[173] See E. Cope, "The origin of the foot structures of Ungulata," _Journ. of Philad. Acad._ 1874. H.F. Osborn, "The evolution of the Ungulate foot," _T. Amer. Phil. Soc._ 1889.

[174] See O.C. Marsh, various papers including "Fossil horses in America," _Amer. Natural._ 1874; "Polydactyl horses," _Amer. J. Sci._ 1879 and 1892. M. Pavlow, "Le développement des Equidés," _Bul. Soc. Moscou_, 1887, and subsequent papers in the same. Osborn and Wortman, "On the Perissodactyls of the White River beds," _Bull. Amer. Mus._ Dec. 23rd, 1895.

[175] See H.F. Osborn, _Chalicotherium and Macrotherium, Amer. Natural._ 1889--91--92.

[176] See p. 409.

[177] See p. 412.

LIST OF AUTHORS REFERRED TO.

Abbott, E.C., 112

Ameghino, F., 351, 424

Andrews, C.W., 299

Balfour, F.M., 16

Ballowitz, E., 424

Bardeleben, K., 504

Bateson, W., 50, 344

Baum, H., 374

Baur, G., 27, 189, 190, 344, 346

Beneden, P.J. van, 353

Benham, W.B., 51

Bettany, G.T., 16, 87, 154

Boulenger, G.A., 169

Brandt, J.F., 352

Bridge, T.W., 123

Brühl, C.B., 210

Burmeister, H., 351, 424

Cope, E.D., 135, 199, 204, 351, 359, 361, 363, 368

Credner, H., 135

Dean, B., 63, 104

Dobson, G.E., 369, 370

Earle, C., 432

Ecker, A., 151

Ellenberger, W., 374

Flower, W.H., 28, 42, 351, 420, 422, 434

Fritsch, A., 135

Fürbringer, M., 295

Gadow, H., 40, 112, 190, 295, 343, 350

Gegenbaur, C., 127

Gervais, P., 353

Günther, A.C.L.G., 70, 104

Haslam, G., 151

Hasse, C., 112, 113

Haswell, W.A., 127

Hertwig, O., 169

Hoffmann, C.K., 190, 202, 210

Howes, G.B., 164, 451

Hubrecht, A.A.W., 104

Hulke, J.W., 192, 204

Hurst, C.H., 71, 297

Hutton, F.W., 299

Huxley, T.H., 11, 13, 133, 135, 191, 210, 295, 297, 334, 343, 351, 374, 437

Kirkaldy, J.W., 51

Klein, E., 11

Kölliker, A., 9

Kükenthal, W., 349, 422

Lankester, E. Ray, 51

Leche, W., 344, 423

Lindsay, B., 336

Lydekker, R., 36, 42, 190, 195, 495

Macbride, E.W., 50

Marsh, O.C., 204, 209, 299, 348, 361, 364, 365, 508

Marshall, A.M., 71, 151

Masterman, A.T., 51

Meyer, H. v., 135

Miall, L.C., 135, 243

Mivart, St G., 369

Morgan, C. Lloyd, 11

Newton, E.T., 283

Osborn, H.F., 348, 420, 429, 508

Owen, R., 191, 204, 210, 297, 348, 351, 420

Parker, T.J., 83, 96, 299

Parker, W.K., 16, 24, 53, 87, 154, 173, 200, 243, 465, 489

Pavlow, M., 358, 508

Pollard, H.B., 119

Poulton, E.B., 422

Pycraft, W.P., 297

Ridewood, W.G., 106, 164

Röse, C., 422

Sagemehl, M., 104

Schäfer, E., 11

Scott, W.B., 368

Seeley, H.G., 191, 212

Selenka, E., 40, 295

Shufeldt, R., 123

Smith, E. Noble, 11

Stirling, E.C., 423

Swirski, G., 103

Taeker, J., 427

Thomas, O., 349, 362, 370, 422, 424, 425

Tomes, C.S., 420

Traquair, R.H., 55, 58

Vogt, C., 297

Wiedersheim, R., 25, 134, 136

Wincza, H., 358, 495

Woodward, A. Smith, 34, 54, 58, 62, 127, 210

Wortman, J.L., 508

Wray, R.S., 303

Zittel, K.A. v., 36, 205, 212

INDEX.

Every reference is to the page: words in italics are names of genera or species; figures in italics indicate that the reference relates to systematic position; figures in thick type refer to an illustration; _f._ = and in following page or pages; _n._ = note.

Aard Vark, _44_, _352_; femur, 517; sacrum, 452; teeth, 425; see _Orycteropus_

Aard wolf, _48_; see _Proteles_

Abdominal ribs, crocodile, 260; reptiles, 286

Abdominal shield, turtle, 215

_Acanthias_, _32_; calcification of vertebrae, 114; pectoral fins, 130

_Acanthodes_, _32_, _64_

Acanthodii, _32_; general characters, 64; spines, 106

_Acanthomys_, _47_; spines, 417

Acanthopterygii, _34_

Accipitres, _41_

Acetabular bone, 25, 513; dog, 409 f.; frog, 165

Acetabulum, 25; crocodile, 266; dog, 409; duck, 324; frog, 165; newt, 149; turtle, 235

_Acipenser_, _32_, 117; exoskeleton, 67; distribution, 66; pectoral fins, 131; plates, 104; skull, 121, =122=; spinal column, 112

Acipenseridae, _32_

Acrodont, defined, 199; teeth of reptiles, 273

_Acrodus_, _32_; teeth, 109

Acromion, dog, 405

_Actinotrocha_, _30_; organ regarded as double notochord, 51

Ad-digital quill, duck, 303

Adjutant, _41_; clavicles, 338

Ægithognathous, 335

Æluroidea, _48_, _369_; teeth, 437

Æpyornis, _40_; tibio-tarsus, 341

Æpyornithes, _40_, _299_

Aftershaft, 328

_Agama_, _38_; teeth, 273

Agamidae, _38_; premaxillae, 284

Aglossa, _36_

Agouti, _48_; see _Dasyprocta_

Agriochoeridae, _45_

_Agriochoerus_, _45_; pes, 525

Ala spuria, duck, 304

Alcidae, _42_; see Auks

Alisphenoid, 19; crocodile, 247; duck, 317; dog, 386

_Alligator_, _39_, _210_, _212_; hyoid, =285=; limbs, =264=; pectoral girdle, =262=; pelvis and sacrum, =267=; scutes, 271; skull, =245=, =248=, =253=

Alligatoridae, 39

_Alytes_, _36_; fronto-parietal fontanelle, 179; vertebrae, 172

Amblypoda, _47_; general characters, 363; manus, 510; pes, 525; skull, 473; teeth, 433; thigh and shin, 519

_Amblystoma_, _35_; skull, 175

American monkeys, _373_; see _Cebidae_

American vultures, _41_; vomers, 335

_Amia_, _33_; distribution, 66; exoskeleton, 67; pectoral fin, 131; scales, 105; skull, 123; tail, 115, 117; vertebrae, 114

Amiidae, _33_

_Ammocoetes_, _31_, _55_

Amphibia, _35_; anterior limb, 185; exoskeleton, 168; general characters, 133; hyoid apparatus, 180; pectoral girdle, 184; pelvic girdle, 187; posterior limb, 188; ribs, 182; skull, 173; sternum, 182; teeth, 169; vertebral column, 170

Amphicoelous, defined, 14

_Amphioxus_, _30_; skeleton, 51 f.; spinal column, 112

_Amphisbaena_, _38_, 272; loss of limbs, 289

Amphisbaenidae, _38_, _200_; pectoral girdle, 288; skull, 277; vertebral column, 275

Amphitheriidae, _43_

_Amphiuma_, _35_, _135_; manus, 187; pes, 188; skull, 174

Amphiumidae, _35_

Anacanthini, _33_

Anal shield, turtle, 215

_Anas_, _41_; _A. boschas_, see Duck

Ankylosis, defined, 12

Angel fish, _32_

Angler, attachment of teeth, 107

Anguidae, _38_

_Anguilla_, _33_; see Eel

_Anguis_, _38_; loss of limbs, 289; scutes, 271

Angular, 22; cod, 100; crocodile, 258; duck, 319; salmon, 94; turtle, 231

Angulo-splenial, frog, 161

Ankle joint, duck, 327; reptiles, 294

Anomodontia, _36_

Anoplotheriidae, _45_

_Anoplotherium_, _45_; manus, 506; pes, 523; tail, 454; teeth, 428

_Anser_, _41_

Anseres, _41_; aftershaft, 329; claws, 330

Anseriformes, _41_

Anteaters, _352_; absence of teeth, 424; manus, 505; pectoral girdle, 495; pelvis, 513; skull, 458; thoraco-lumbar vertebrae, 447; Spiny --, _43_; Great and Two-toed --, _44_

Antelope, _359_; manus, 507; Four-horned A., _46_

Anterior limb, 26; Amphibia, 185; birds, 338; crocodile, 263; dog, 405; duck, 322; frog, 164; newt, 147; reptiles, 290; turtle, 232

Anthropoid apes, _373_; arm-bones, 503; pelvis, 515

Anthropoidea, 49; general characters, 372; sacrum, 452; skull, 482; teeth, 441

_Anthropopithecus_, _49_; ribs, 493

Antiarcha, _31_; general characters, 55

Antibrachium, see fore-arm

_Antilocapra_, _46_; horns, 417

Antilocapridae, _46_

Antitrochanter, duck, 325

Antlers, 8, 358; Cervidae, 469

Antorbital process, 18

Anura, _36_; general characters, 136; hyoid apparatus, 180; pelvis, 187; posterior limb, 188; skull, 179; sternum, 182; vertebrae, 172

_Apatornis_, _40_; vertebrae, 332

Apteria, 328

Apteryges, _40_

_Apteryx_, _40_, _299_; aftershaft, 329; anterior nares, 333; claws, 330; foot, 342; manus, 338; pectineal process, 341; pectoral girdle, 338; pneumaticity of skeleton, 331; _A. oweni_, pelvic girdle and sacrum, =340=

Aqueductus vestibuli, dogfish, 74

Arcade: infratemporal--, crocodile, 255; _Sphenodon_, 283; inner --, duck, 318; outer --, duck, 318; supratemporal --, crocodile, 257; reptiles, 281

Archaeoceti, _44_; general characters, 356; skull, 461; teeth, 426

_Archaeopteryx_, _40_, _297_; claws, 330; fibula, 341; mandible, 335; metatarsals, 342; pelvis, 341; ribs, 336; sacrum, 333; skull, 333; tail, 333; teeth, 330; wing, 338

Archaeornithes, _40_; characters, 297

_Archegosaurus_, _35_, _136_; palatines, 177

Archipterygium, _Ceratodus_, 127; Ichthyotomi, 62

Arcifera, _36_, 185

Arctoidea, _48_, 369; teeth, 438

_Ardea_, _41_; see Heron

Ardeae, _41_

Arm, see fore-arm and upper arm

Armadillo, _44_, _352_; cervical vertebrae, 443; femur, 517; humerus, 501; lumbar vertebrae, 447; manus, 505; pectoral girdle, 495; pelvis, 513; ribs, 491; sacrum, 452; scales, 417; scutes, 419; skull, 459; teeth, 424

Armour plates, 8

Arthrodira, _34_; characters, 70

Articular, 22; cod, 100; crocodile, 258; duck, 319; newt, 144; salmon, 94; turtle, 231

Artiodactyla, _45_; characters, 358; manus, 506; odontoid process, 445; pes, 522; ribs, 491; skull, 465; teeth, 427; thoraco-lumbar vertebrae, 448

Asses, _360_

_Asterolepis_, _31_, _55_

Asterospondyli, 114

Astragalus, 27; crocodile, 268; dog, 414; mammals, 521

Astrapotheriidae, _46_

_Astrapotherium_, _46_, 361; dental formula, 432; femur, 519; pes, 525

_Ateles_, _49_; pollex, 512; tail, 454

Atlantosauridae, _38_

Atlas, 15; crocodile, 240; dog, =379=, 380; duck, 309; ox, =445=; turtle, 219

Attachment of teeth, 4; in fish, 107

_Auchenia_, _45_; see Llama

Auditory aperture or meatus: external --, crocodile, 250; dog, 402; turtle, 228; internal --, crocodile, 246, 251; dog, 392; turtle, 228

Auditory capsule, 20; cod, 96; crocodile, 250; dog, 390; dogfish, 74; frog, 156; newt, 143; turtle, 227

Auditory ossicles, crocodile, 251; dog, 393; duck, 320; mammals, 485 f.; turtle, 228

Auks, _42_; thoracic vertebrae, 332

Autostylic, 61, 119

Aves, _40_; characters, 295; see Birds

Axial skeletal rods, 50

Axial skeleton, crocodile, 239; cod, 83; dog, 377; dogfish, 72; duck, 307; frog, 152; newt, 138; turtle, 218

Axis vertebra, crocodile, 241; dog, 380; duck, 309; turtle, 220

Axolotl, _35_; see _Siredon_

Aye Aye, _49_; see _Chiromys_

_Babirussa_, _45_; dental formula, 428

Baboon, _49_; see _Cynocephalus_

_Balanoglossus_, _30_, 50

_Balaena_, _44_, _357_; scapula, 495; _B. mysticetus_ baleen, 419

Balaenidae, _44_

Balaenoidea, _44_; general characters, 356

_Balaenoptera_, _44_, 357; manus, 506; thoracic vertebrae, 448; scapula, 495; _B. musculus_, cervical vertebrae, =444=

Baleen, 3, 418

_Balistes_, _33_; teeth, 111

Balistidae, _33_

Ball and socket joints, 13

Bandicoot, _43_

Barb, 302

Barbule, 303

Barramunda, _34_; see _Ceratodus_

Basalia, dogfish, 79

Basibranchial, dogfish, 78; cod, 101; duck, 320; newt, 145; salmon, 95

Basi-branchiostegal, cod, 101; salmon, 95

Basicranial axis, 19; dog, 384

Basidorsalia, dogfish, 72

Basi-hyal, dogfish, 78; dog, 399; duck, 320

Basilar plate, 17

Basilingual plate, Anura, 180; crocodile, 259; frog, 161; turtle, 231

Basi-occipital, 19; crocodile, 246; cod, 97; dog, 386; duck, 315; salmon, 89; turtle, 224

Basipterygium, cod, 103; dogfish, 82

Basisphenoid, 19; crocodile, 247; dog, 386; salmon, 91; turtle, 225

Bastard wing, duck, 304

Bathyerginae, palate, 366

_Bathyergus_, _47_; auditory ossicles, 488; manus, 511

Batoidei, _32_, 64

_Batrachoseps_, _35_; teeth, 169

Bats, claws, 418; Horseshoe bats, _49_; see Chiroptera

_Bdellostoma_, _31_, _55_; teeth, 57

Beak, 3; birds, 329; duck, 302; _Siren_, 168; tadpoles of Anura, 168; turtle, 215

Bears, _48_, _369_; manus, 511; pes, 526; sacral vertebrae, 452; skull, 479; Isabelline -- mandible, =438=

Beaver, _47_; fibula, 520; humerus, 502; pes, 526; sacrum, 452; tail, 454

_Belodon_, _39_, 211; frontals, 277; palate, 281; vertebrae, 275

Bichir, _33_; see _Polypterus_

Bicipital groove, dog, 405

Bilophodont, defined, 345; teeth of Tapiridae, 429

_Bipes_, _38_; limbs, 289

Birds, anterior limb, 338; endoskeleton, 331 f.; exoskeleton, 328 f.; general characters, 295; hyoid, 336; pectoral girdle, 336; pelvic girdle, 339; posterior limb, 341; ribs, 336; skull, 333; sternum, 336; teeth, 330; vertebral, 332

_Bison_, _46_; occipital crest, 468

Blind snake, _38_; see _Typhlops_

Blind worm, _38_; see _Anguis_

Boidae, _38_

_Bombinator_, _36_; vertebrae, 172

Bone, development of, 10 f.

Bone cells, 10

Bony Ganoids, fins, 105; pelvic fin, 132; ribs, 126; skull, 123; vertebral column, 114; see _Holostei_

Border: alveolar --, of dog's jaw, 398; coracoid, glenoid, and suprascapular -- of dog's scapula, 405

_Bos_, _46_; occipital crest, 468; ribs, 491; see Ox

Bottlenose, _44_; see _Hyperoödon_

Bovidae, _46_; pes, 523; skull, 468

Bow-fin, _33_; see _Amia_

Brachial ossicles, cod, 103

Brachium; see upper arm

Brachydont, defined, 345; teeth of Ungulates, 429 f.

_Brachycephalus_, _36_; bony plates of, 168

Brain case, crocodile, 245; dog, 384; duck, 314; frog, 154; newt, 140; turtle, 224

Bradypodidae, _43_; see Sloths

_Bradypus_, _43_; cervical vertebrae, 443; pectoral girdle, 495; skull, 457; thoraco-lumbar vertebrae, 447

Branchial arches, Amphibia, 180 f.; cod, 101; dogfish, 78; fish, 120 f.; newt, 145; salmon, 95; -- basket, Marsipobranchii, 38; -- skeleton, _Amphioxus_, 52; Balanoglossus, 50

_Branchiosaurus_, _35_; branchial arches, 180

Branchiostegal rays, cod, 100

_Brontops_, _46_; see _Titanotherium_

_Brontosaurus_, _38_, _207_; sternum, 288

_Bubalus_, _46_; ribs, 491; see Buffalo

Buccal skeleton, _Amphioxus_, 52

_Buceros_, _42_; see Hornbill

Buckler, of Labyrinthodonts, 168, 184

Buffalo, _46_; Cape --, skeleton of, =492=

_Bufo_, _36_; hyoid, 182; jaws, 169; _B. viridis_, carpus, 186

Bufonidae, _36_

Bunodont, defined, 345; teeth of Ungulata, 427 f.

Buno-selenodont, defined, 432

Caeciliidae, _35_

_Caiman_, _39_; _C. latirostris_ hyoid, =285=, limbs, =264=, lateral view of skull, =248=, palatal view of cranium and mandible, =245=, longitudinal section of skull, =253=, pectoral girdle, =262=, pelvic girdle and sacrum, =267=; _C. sclerops_, scutes, 271

Ca'ing whale, _45_; see _Globicephalus_

_Calamoichthys_, _33_; distribution, 66

Calamus, 302

Calcaneum, 27; crocodile, 268; dog, 414

Calcar, of frog, 167

_Callorhynchus_, _32_, _66_; teeth, 110

Camel, _45_, _359_; manus, 507; teeth, 428

Camelidae, _45_

_Camelus_, _45_; see Camel

Camptosauridae, _39_

Canal: alisphenoid --, dog, 402; carotid --, duck, 315; Eustachian --, crocodile, 247; dog, 402; duck, 316; interorbital --, dogfish, 76

Canaliculi, 10

Canidae, _48_; humerus, 502; skull, 479; see Dog

Canine, 344; dog, 376 f.

_Canis_, _48_; thoraco-lumbar vertebrae, 450; see Dog

_Capitosaurus_, _35_; skull, =176=

Capybara, _48_; manus, 511; pes, 526; skull, 476; tail, 454

Carapace, Chelonia, 271; _Dermochelys_, 272; Glyptodonts, 419; Green turtle, 215; Loggerhead turtle, =216=

Carcharidae, _32_

Carina sterni, duck, 321

Carinatae, _40_; general characters, 300; quadrate, 334

Carnassial teeth, 368; carnivora, =436=; dog, 376 f.

Carnivora, _48_; arm bones, 502; auditory ossicles, 488; cervical vertebrae, 446; general characters, 367; manus, 511; pelvis, 515; pes, 526; ribs, 493; sacral vertebrae, 452; skull, 478; sternum, 490; tail, 454; teeth, 437; thigh and shin, 520; thoraco-lumbar vertebrae, 450

Carnivora vera, _48_; general characters, 368; scapula, 497

Carp, _33_; pharyngeal teeth, 111

Carpo-metacarpus, duck, 324

Carpus, 26; crocodile, 265; dog, 408; duck, 323; frog, 164; newt, 147; turtle, 233

Cartilage, structure of, 10

Cartilaginous ganoids, cranium, 121; pelvic fin, 132; spinal column, 112; see Chondrostei

Cassowary, _40_, _299_; aftershaft, 328; bony crest, 334; claws, 330; pelvic girdle and sacrum, =340=; secondaries, 329

_Castor_, _47_; see Beaver

Castoridae, _47_

_Casuarius_, _40_; see Cassowary

Cataphracti, _34_

Cat, _48_, _369_; hallux, 526; manus, 511; skull, 479

Cat-fish, _33_

Cathartae, _41_

_Cathartes_, _41_; see American vulture

Caudal fin, Cetacea, 453; fish, 116; -- vertebrae, crocodile, 243; cod, 85; dog, 383; duck, 312; general characters, 16; newt, 140; turtle, 222

_Cavia_, _48_; tail, 454

Caviidae, _48_

Cebidae, _49_, _373_; ribs, 493; skull, 484; teeth, 441

_Coenolestes_, _43_, 424

Cement, 5

_Centetes_, _49_; caudal vertebrae, 454; pelvic symphysis, 515; spines, 417; teeth, 440; thoraco-lumbar vertebrae, 450

Centetidae, _49_; auditory ossicles, 488; skull, 480

Centrale, 27; see Carpus and Tarsus

Centre of motion, 448

Centrum, 14

_Cephalaspis_, _31_, _55_

Cephalic shield, armadillos, 419

_Cephalochordata_, _30_, 51

_Cephalodiscus_, _30_, 50

_Ceratodus_, _34_, _70_; branchial arches, 124; cranium, =125=; skeleton, =128=; skull, 117, 124; spinal column, 113; teeth, 111

Cerato-branchial, cod, 101; dogfish, 78; duck, 320; salmon, 95

Cerato-hyal, 23; cod, 100; dog, 399; dogfish, 78; salmon, 95

_Ceratophrys_, _36_; bony plates of, 168; teeth, 170

_Ceratops_, _39_; see _Polyonax_

Ceratopsia, _39_; characters, 209; premaxillae, 284

Ceratopsidae, _39_

_Ceratosaurus_, _38_, 208; supratemporal fossae, 283; _C. nasicornis_, skeleton, =206=

Cercopithecidae, _49_, _373_

Cervical ribs, crocodile, 260; reptiles, 285

Cervical vertebrae, crocodile, 239; dog, 380; duck, 307; general characters, 15; mammals, 442; turtle, 219

Cervidae, _46_; skull, 469

_Cervulus_, _46_; pes, 523

_Cervus_, 46; _C. megaceros_, antlers, 469

_Cestracion 32_; calcification of vertebrae 114; external branchial arches 121; pectoral fin 130; skull =118=; suspensorium 119; teeth 109; vertebral column 114

Cestraciontidae _32_

Cetacea _44_, 522; arm bones 501; auditory ossicles 487; caudal vertebrae 453; cervical vertebrae 444; characters 353; exoskeleton 416 f.; hind limb 518; manus 505; pectoral girdle 495; pelvis 514; position of limbs 28; ribs 491; skull 461 f.; sternum 489; teeth 426; thoraco-lumbar vertebrae 448

Cetiosauridae _38_

_Chalcides_ _38_; limbs 289

Chalicotheriidae _46_; femur 519; manus 509

_Chalicotherium_ _46_; femur 360; pes =508=, 525; teeth 432

_Chamaeleon_ _38_, 199 f.; epipubis 293; ilia 291; manus 291; skull 278

Chamaeleonidae _38_

Charadriidae _42_

Charadriiformes _42_

_Chauna_ _41_; interorbital septum 333; ribs 336; _C. derbiana_, spurs 330

_Chelone_ _37_, _194_; plastron 271, =218=; see Turtle

Chelonia _37_; beaks 271; carapace 271; general characters 193; humerus 290; limbs 290; palate 281; pectoral girdle 288; pelvic girdle 291; skull 277 f.; tarsus 293; vertebrae 275 f.

Chelonidae _37_

Chelydae _37_

_Chelydra_ _37_; carpus 26, 291

Chelydridae _37_

_Chelys_ _37_, _195_

Chersidae _37_

Chevron bones 16; crocodile 243; mammals 453 f.; reptiles 276

Chevrotain _45_, _359_; teeth 429

_Chimaera_ _32,_ _66_; attachment of fins 130; pelvic girdle 127; skull =65=; teeth 110

Chimaeridae _32_

Chimaeroidei, general characters 65

Chimpanzee _49_; carpus 512; ribs 493; thoraco-lumbar vertebrae 450

_Chinchilla_ _47_; auditory ossicles 488

Chinchillidae _47_

Chiromyidae _49_

_Chiromys_ _49,_ _372_; manus 512; pes 527; teeth 441

Chiroptera _49_; auditory ossicles 488; arm bones 503; cervical vertebrae 446; general characters 370; manus 512; pelvis 515; pes 527; sacrum 452; shoulder girdle 499; skull 481; sternum 490; tail 454; teeth 440; thigh and shin 520; thoraco-lumbar vertebrae 450

_Chirotes_ _38_; limbs 289

_Chlamydophorus_ _44,_ _272_; scutes 419; skull 459

_Chlamydoselache_ _31_; branchial arches 121

_Choeropus_ _43_; manus 504; pes 522

_Choloepus_ _43_; ribs 491; shifting of pelvis 451; skull =458=; sternum 489; thoraco-lumbar vertebrae 447; _C. hoffmanni_ cervical vertebrae 443

Chondrocranium, salmon 87

Chondroid tissue, _Balanoglossus_ 50

Chondrostei _32_; fins 105; general characters 67; teeth 110; see Cartilaginous ganoids

Chordal sheath, _Amphioxus_ 52

Chrysochloridae _49_

_Chrysochloris_ _49_; auditory ossicles 488; claws 418; teeth 440

_Ciconia_ _41_; see Stork

Ciconiiformes _41_

Cingulum 376

Civet _48,_ _369_; teeth 437

_Cladoselache_ _31,_ _63_; fin 129

Clasper 132; dogfish 82

Clavicle 25; birds 338; cod 102; duck 322; dog 405; fish 126; frog 163; mammals 494 f.; reptiles 289

Claws 3; birds 330; crocodile 237; dog 374; duck 302; mammals 417; turtle 215

Clupeidae, _33_

_Clupeus_, _33_

Cnemial crest, dog, 412; duck, 326

_Coccosteus_, _34_, _70_

Coccyx, man, 454

Cochliodontidae, _31_

_Cochliodus_, _31_; dental plates, 109

Cod, _33_; appendicular skeleton, 101 f.; cranium, 96; mandibular and hyoid arches, =99=; median fins, 86; pectoral girdle and fin, =102=; ribs, 86; skull, 96 f.; vertebral column, 83 f.

_Coelogenys_, _48_; zygomatic arch, 477

_Coenolestes_, _43_, 424

Coffer-fish, _33_; see, _Ostracion_

_Colobus_, _49_; pollex, 512

Colubridae, _38_

Columbae, _42_

Columbidae, _42_

Columella, crocodile, 251; duck, 320; frog, 157; turtle, 228

Columella cranii, 200 n; see epipterygoid

Colymbi, _40_

Colymbiformes, _40_

Compsognathidae, _38_

_Compsognathus_, _38_, 208

Condylar ridge, duck, 326

Condyle of humerus, dog, 406; of mandible, dog, 398

Condylarthra, _47_; femur, 519; general characters, 361; manus, 509; skull, 472; teeth, 432

Contour feather, duck, 303

Copula, 23

_Coracias_, _42_; see Roller

Coraciae, _42_

Coraciiformes, _42_

Coracoid, 25; cod, 103; crocodile, 263; duck, 322; frog, 163; Monotremata, 493; newt, 147; reptiles, 288; turtle, 232

Coracoid groove, duck, 321

Cormorant, _41_; foot, 342; skull, 335

Cornu, see hyoid

Cornua trabeculae, 18

_Coryphodon_, _47_; femur, 519; manus, 510; pes, 525; skull, 473; teeth, 433; _C. hamatus_, manus, =510=

Coryphodontidae, _47_

Costal plate, turtle, 215; -- process, duck, 321; -- shield, turtle, 214

Cotyloid bone, 25, 513; see Acetabular bone

Cotylopidae, _45_

_Cotylops_, _45_; pollex, 506; skull, 468

Coverts, 306, 328

Cranium, 18; cod, 96 f.; crocodile, 244 f.; development of, 16 f.; dog, 384 f.; dogfish, 73 f.; duck, 314; frog, 154 f.; newt, 140 f.; turtle, 222 f.

Cranio-facial axis, dog, 384

Creodonta, _48_; carpus, 512; femur, 520; general characters, 368; skull, 479; teeth, 439

Cribriform plate, dog, 388, 400

Crocodile, _210_, _212_; anterior limb, 263; exoskeleton, 237; pectoral girdle, 262; pelvic girdle, 266; posterior limb, 268; ribs and sternum, 259; skeleton, 237 f.; skull, 243 f.; tarsus, 293; teeth, 238; vacuities in surface of cranium, 256; vertebral column, 239

Crocodilia, _39_; general characters of, 210; palate, 281; skull, 277 f.; succession of teeth, 274; teeth, 273

Crocodilidae, _39_

_Crocodilus_, _39_; _C. palustris_, sternum and associated bones, =261=; late thoracic and first sacral vertebrae, =242=; _C. vulgaris_, cervical vertebrae, =239=

Crossopterygii, _33_; general characters, 68

Crotalidae, _38_

_Crotalus_, _38_; jaws 280; see Rattlesnake

Crows, _42_

Crura of stapes, dog, 393

Cruro-tarsal, ankle joint, 345

Crus, 26; crocodile, 268; dog, 412; duck, 326; frog, 166; newt, 149; turtle, 235

Crusta petrosa, 5

_Cryptobranchus_, _35_, 135; skull, 175; _C. lateralis_, sacral vertebrae, 171

Cryptodira, _37_; characters, 194

Ctenoid scales, 8, 60, 105

Cubitals, 303 f.

Cuboid, 27; dog, 415

Cuckoo, foot, 342

Cuculi, _42_

Cuculiformes, _42_

Cuneiform bones, 27; dog, 414 f.

_Cyclodus_, _38_; see _Tiliqua_

Cycloid scales, 8, 60, 105; cod, 83

_Cyclopidius_, _45_; skull, 468

Cyclospondyli, 114

Cyclostomata, _31_; general characters, 53

_Cycloturus_, _44_; hallux, 522; manus, 505

_Cygnus_, _41_; see Swan

_Cynocephalus_, _49_; cervical vertebrae, 446; skull, 482

Cynoidea, _48_, _369_; dental formula, 437

_Cynognathus_, _36_; occipital condyle, 277; teeth, 273

Cyprinidae, _33_

_Cyprinus_, _33_; see Carp

Cypseli, _42_

Cypselidae, _42_; see Swifts

Cystignathidae, _36_

_Dactylopterus_, _34_; pectoral fins, 131

Dasypodidae, _44_

_Dasyprocta_, _48_; auditory ossicles, 488; thoraco-lumbar vertebrae, 450

Dasyproctidae, _48_

_Dasypus_, _44_; manus, 505; skull, 459; stapes, 487; teeth, 424

Dasyuridae, _43_, _350_; dentition, 423; pes, 521; skull, 456

Deer, _359_; manus, 507; pes, 523; Chinese water --, _46_, see _Hydropotes_; Musk --, _46_, see _Moschus_; Red -- fibula, 519

Delphinidae, _45_

_Delphinus_, _45_, 357; lumbar vertebrae, 448; skull, 462 f.

Deltoid ridge, crocodile, 263; dog, 406; frog, 164

_Dendrohyrax_, 363

Dental formula, regular, 344, 422; Anthropoidea, 441; _Astrapotherium_, 432; _Babirussa_, 428; Camel, 428; _Chiromys_, 441; Chiroptera (many), 440; Cynoidea, 437; _Dinotherium_, 434; Dog, 376; Duplicidentata, 435; _Elephas_, 434; _Erinaceus_, 440; _Felis_, 437; _Galeopithecus_, 440; _Hippopotamus_, 427; Horse, 430; _Hydromys_, 436; Hyracoidea, 362; Macropodidae, 423; _Manatus_, 425; _Notoryctes_, 423; _Otaria_, 439; _Procavia_, 432; _Pteropus_, 441; Rodentia (most), 435; Ruminantia, 429; _Squalodon_, 427; _Sus_, 428; Tapiridae, 429; _Thylacinus_, 423; _Uintatherium_, 433; _Ursus_, 439; _Zeuglodon_, 426

Dentary, 22; crocodile, 258; cod, 100; duck, 320; frog, 161; newt, 144; salmon, 94; turtle, 230

Dentine, 5

Derbian Screamer, spurs, 330

Dermal exoskeleton, crocodile, 237; fish, 105; mammals, 419; reptiles, 271; turtle, 215

Dermo-supra-occipital, Labyrinthodontia, 177; _Polypterus_, 122

Dermochelydidae, _37_

_Dermochelys_, _37_, _194_, 214, 270; carapace and plastron, 272

Dermoptera, _48_; general characters, 370

Derotremata, _35_

_Desmodus_, _49_; teeth, 441

Desmognathous, 319, 335

Development of bone, 10; of cranium, 16; of teeth, 7

_Dicynodon_, _36_, _192_; beak, 271; supratemporal fossa, 283; teeth, 273

Didelphia, _43_; general characters, 349

Didelphyidae, _43_, _350_; auditory ossicles, 486; pes, 521; teeth, 423

_Didelphys_, _43_; atlas, 443; teeth, 422

_Didus_, _42_; see Dodo

Digitigrade, defined, 358 n.

Digits, _26_; see Manus and Pes

_Dimetrodon_, _36_; thoracic vertebrae, 276

_Dinichthys_, _34_, _70_

Dinocerata, 364; see Uintatheriidae

Dinornithes, _40_, _299_; see Moas

Dinosauria, _38_; general characters, 204; humerus, 290; ischium, 291; pectoral girdle, 288; pes, 293; pre-orbital vacuity, 284; ribs, 285; vertebrae, 275 f.

Dinotheriidae, _47_

_Dinotherium_, _47_, 365; dental formula, 434; teeth, 345

_Diodon_, _33_; beaks, 111; _D. hystrix_, scales, 105

Diphycercal tail, 60, 116

Diphyodont, defined, 7, 344

_Diplacanthus_, _32_, _64_

Dipneumona, _34_

Dipnoi, _34_; general characters, 69; pelvic fins, 131; skull, 124; spinal column, 113; tail, 116; teeth, 111

Dipodidae, _47_

Diprotodont, 423

Diprotodontia, _43_; characters, 350

Dipteridae, _34_, _70_; cranium, 124; tail, 117; teeth, 111

_Dipus_, _47_; cervical vertebrae, 446; pes, 526

Discoglossidae, _36_

_Discoglossus_, _36_; ribs, 182; vertebrae, 172

Distal, defined, 23 n.

Divers, _40_; thoracic vertebrae, 332

_Docidophryne_, _36_; shoulder girdle and sternum, =183=

Dodo, _42_; wing, 338

Dog, _48_; arm bones, =407=; anterior limb, 405; atlas and axis, =379=; cranium, 384, =389=, =396=; dentition, =375=; innominate bone, =410=; leg bones, =411=; manus, 408, =413=, 511; pectoral girdle, 404; pelvic girdle, 409; pes, =413=, 414; posterior limb, 412; ribs, 402; second lumbar vertebra, =382=; second thoracic vertebra, =382=; skull, 383, =387=; sternum, =403=, 404; vertebral column, 378

Dogfish, _64_; cranium, 73; exoskeleton, 71; median fins, 79; pectoral girdle and fin, 79; pelvic girdle, 81; pelvic fin, 81; ribs, 73; skull, 73, =75=; vertebral column, 72; visceral skeleton, 77; Spotted and Spiny --, _32_

Dolphin, _45_, _357_; lumbar vertebrae, 448; Gangetic --, _45_, see _Platanista_

Donkey, skull, =431=

_Dorcatherium_, _45_; manus, 507

Dorsal vertebra, 16

Dorsal shield, crocodile, 238

Down feathers, 306

_Draco_, _38_; ribs, 286

Dromaeognathous, 335

_Dromaeus_, _40_, _299_; see Emeu

Duck, _41_, 334; beak, 329; claws, 330; cranium, =313=; exoskeleton, 302; pectoral girdle, 321; pelvic girdle, 324, =311=, =325=; pes, 327; posterior limb, 326; ribs, 320; skull, 312, =312=, =313=; sternum, 321; vertebral column, 307; wing, 322, =304=, =305=

Duckbill, _43_; see _Ornithorhynchus_

Dugong, _44_; humerus, 501; pelvis, 514; thoraco-lumbar vertebrae, 448; see _Halicore_

Duplicidentata, _48_, 366; dental formula, 435; skull, 478

Eagles, 335

Eared Seals, _369_; scapula, 498; see Otariidae

_Echidna_, _43_; caudal vertebrae, 453; manus, 504; pelvis, 513; sacral vertebrae, 451; shoulder-girdle and sternum, =494=; skull, 455; spines, 417; spur, 418; thoraco-lumbar vertebrae, 447

Echidnidae, _43_; pes, 521

Ectethmoid, 21 n.

Ectocondylar ridge, dog, 406

Edentata, _43_; auditory ossicles, 487; arm bones, 500; caudal vertebrae, 453; cervical vertebrae, 443; manus, 504; pectoral girdle, 495; pes, 522; pelvis, 513; ribs, 491; sacrum, 452; skull, 457; sternum, 489; teeth, 424; thigh and shin, 517; thoraco-lumbar vertebrae, 447

Eel, _33_; scales, 105

Elasmobranchii, _31_; cranium, 118 f.; clasper, 132; general characters, 61; pelvic fins, 131; ribs, 125; teeth, 109; vertebral column, 113 f.; visceral arches, 120

_Elasmotherium_, _46_; mesethmoid, 470

Elephant, _47_; auditory ossicles, 487; caudal vertebrae, 453; ribs, 491; skull, 473 f., =474= and =475=; tusks, 420; see also Proboscidea

Elephantidae, _47_

_Elephas_, _47_, _364_; dental formula, 434; _E. planifrons_, 435; see Elephant

_Elginia_, _36_; skull, 191, 283

Embolomerous, 172

Emeu, _40_, _299_; aftershaft, 328; claws, 330

Enamel, 4; -- cap, 7; -- organ, 7

Endochondral ossification, 11

Endoskeleton, Amphibia, 170; birds, 331 f.; cod, 83 f.; crocodile 239, f.; dog, 377 f.; dogfish, 71 f.; duck, 306 f.; fish, 112 f.; frog, 151 f.; mammals, 442 f.; newt, 138 f.; reptiles, 275 f.; turtle, 218 f.

Engystomatidae, _36_

Entoplastron, turtle, 217

Epanorthidae, _43_, _350_

Epi-branchial, cod, 101; dogfish, 78; salmon, 94

Epicoracoid, 25; frog, 163; turtle, 232; Monotremes, 493; vestiges of in Rodentia, 497

_Epicrium_, _35_; orbit, 179

Epidermal exoskeleton, birds, 328; crocodile, 237; dog, 374; duck, 302; mammals, 416; reptiles, 270; turtle, 214

Epi-hyal, cod, 100; dog, 399; salmon, 94

Epi-otic, 20; cod, 96; crocodile, 250; Labyrinthodontia, 177; reptiles, 278; salmon, 89; turtle, 227

Epiphysis, 11

Epiplastron, turtle, 217

Epiprecoracoid, Amphibia, 184; turtle, 232

Epipterygoid, Lacertilia, 200; reptiles, 278

Epipubis, crocodile, 267; newt, 149; turtle, 235

Episternum, 217; frog, 163

Equidae, _46_; mane, 416; scapula, 496; skull, 471

_Equus_, _46_; see Horse

Erinaceidae, _49_

_Erinaceus_, _49_; dental formula, 440; pelvic symphysis, 515; presternum, 490; see Hedgehog

Esocidae, _33_

Esox, _33_; attachment of teeth, 107

Ethmoid, 394; see median ethmoid

Ethmoidal plane, 390; -- region, 21

Ethmo-palatine ligament, dogfish, 77

Ethmo-turbinal, dog, 395

_Euchirosaurus_, _35_; vertebrae, 171

Eustachian canal, see Canal

Eusuchia, _39_; general characters, 212

Eutheria, _43_; general characters, 351

_Exocaetus_, _33_; pectoral fins, 131

Exoccipital, 19; cod, 97; crocodile, 246; dog, 386; duck, 314; frog, 154; newt, 141; salmon, 89; turtle, 224

Exoskeleton, 2; Amphibia, 168; birds, 328; crocodile, 237; dog, 374; dogfish, 71; duck, 302; fish, 104; ganoids, 66; mammals, 442; reptiles, 270; turtle, 214

Extensor side, defined, 29

Extra-branchial, dogfish, 79

Extra-columella, crocodile, 251; turtle, 228

Fabella, dog, 412

_Falco_, _41_

Falcon _41_, 335

Falconiformes, _41_

Feathers, 3, 328; duck, 302

Felidae, _48_; claws, 418

_Felis_, _48_; dental formula, 437; thoraco-lumbar vertebrae, 450

Femoral shield, turtle, 215

Femur, 26; crocodile, 268; dog, 412; duck, 326; frog, 166; mammals, 517 f.; newt, 149; ox and rhinoceros, =518=; turtle, 235

Fenestra ovalis, crocodile, 250 f.; dog, 392; duck, 316; frog, 157; turtle, 228; -- rotunda, dog, 392; duck, 316

Fenestral recess, duck, 316

Fibula, 26; crocodile, 268; dog, 412; duck, 327; frog, 166; newt, 149; turtle, 235

Fibulare, 27; see Tarsus

File-fish, _33_; see _Balistes_

Filoplume, 306

Finches, _42_

Fins, fish, 115; caudal --, Cetacea, 453; cod, 87; fish, 116; Ichthyosauria, 195; median --, cod, 86; dogfish, 79; pectoral --, cod, 103; dogfish, 79; pelvic --, cod, 103; dogfish, 81

Fin-rays, 105, 115; cod, 83, 103; dogfish, 79

Firmisternia, _36_, 185

Fish, appendicular skeleton, 126; endoskeleton, 112 f.; exoskeleton, 104; general characters, 60 f.; paired fins, 127 f.; ribs, 125 f.; skull, 117 f.; spinal column, 112 f.; teeth, 106 f.

Fissipedia, _48_; general characters, 368

Flamingo, 335

Flexor side, defined, 29

Floating ribs, dog, 402; mammals, 490

Flower, Sir W.H., on succession of teeth in elephants, 434

Flying-fish, _33_; -- fox, _49_, _371_, skull, 481, see _Pteropus_; -- gurnard, _34_, see _Dactylopterus_; -- lemur, _48_, see _Galeopithecus_; -- lizard, _38_, see _Draco_

Fontanelle, salmon, 89; anterior --, dogfish, 74; frog, 154; posterior --, frog, 154

Foot, crocodile, 269; dog, 414; frog, 167; newt, 149 f.; turtle, 236

Foramen: anterior palatine --, dog, 401; condylar --, dog, 401; -- cordiforme, reptiles, 292; ect-epicondylar --, _Sphenodon_, 290; ent-epicondylar --, 191 n.; Carnivora vera, 502; Cebidae, 503; _Choloepus_, 500; Condylarthra, 362, 502; Creodonta, 368; Insectivora, 503; Lemurs, 503; Marsupials, 500; reptiles, 290; external mandibular --, crocodile, 258; inferior dental --, dog, 399; infra-orbital --, dog, 401; Rodents, 477; ilio-sciatic --, duck, 325; internal mandibular --, crocodile, 258; internal orbital --, dog, 401; interparietal --, Labyrinthodontia, 173, 177; reptiles, 277; -- lacerum anterius, dog, 388, 400; -- lacerum medium, dog, 402; -- lacerum posterius, dog, 392, 401; lachrymal --, dog, 394, 401; -- magnum, cod, 97; crocodile, 257; dog, 386, 402; dogfish, 76; duck, 314; frog, 154; newt, 141; salmon, 89; turtle, 224; mental --, dog, 399; obturator --, duck, 326; dog, 410; ophthalmic --, dogfish, 74; optic --, dog, 400; dogfish, 74; orbitonasal --, dogfish, 74; -- ovale, crocodile, 249; dog, 400; pneumatic --, duck, 323; pneumogastric --, dogfish, 76; posterior palatine --, dog, 401; postglenoid --, dog, 402; pre-acetabular --, Chiroptera, 515; -- rotundum, dog, 400; stylomastoid --, dog, 392 f., 400; thyroid --, dog, 410; trigeminal --, duck, 316; -- triosseum, duck, 322

Fore-arm, 26; crocodile, 265; dog, 406; duck, 323; frog, 164; newt, 147; turtle, 233

Fossa: cerebellar --, dog, 392; cerebral --, dog, 392; digital --, dog, 412; floccular --, dog, 392; infratemporal --, see lateral temporal --; lachrymal --, Ruminants, 469; lateral temporal --, crocodile, 257; _Sphenodon_, 283; olecranon --, dog, 406; prescapular --, dog, 405; postscapular --, dog, 405; post-temporal --, _Sphenodon_, 283; pterygoid --, crocodile, 257; suborbital --, Ruminants, 469; supra-acetabular --, Ruminants, 514; supratemporal --, crocodile, 249, 256; reptiles, 283; supra-trochlear --, dog, 406; temporal --, dog, 398; trochanteric --, dog, 412

Fowl, _41_, 335; claws, 330; skeleton, =301=

Fox, _48_

Frigate bird, _41_; clavicles, 338

Frog, anterior limb, 164; cranium, =155=, =157=; hyoid apparatus, 161; pelvic girdle, 165; posterior limb, 166; shoulder-girdle and sternum, =183=; skull, 154 f., =155=, =159=; teeth, 151; vertebral column, 152; Common --, Edible --, Fire-bellied --, Green-tree --, Horned --, Midwife --, Painted -- and Toad --, _36_;

Frontal, 19; cod, 96; crocodile, 249; dog, 388; duck, 314; newt, 141; salmon, 91; turtle, 225; -- segment, crocodile, 249; dog, 388; turtle, 225

Fronto-parietal, frog, 156

Frugivorous bats, manus 512; see Pteropidae

Fulcra 67; _Polypterus_ 106

Furcula 296; duck 322

Gadidae _33_

_Gadus_ _33_; see Cod

Galeopithecidae _48_

_Galeopithecus_ _48_, _370_; dental formula 440; inter centra 450; pelvic symphysis 515; skull 480

_Galesaurus_ _36_, _192_; teeth 273

_Galeus_, _32_; occipital joint 118

Galli _41_

Galliformes _41_

_Gallus_ _41_; _G. bankiva_ skeleton =301=

Gannet, _41_; wing =339=

Ganoid scales 8, 60, 104

Ganoidei _32_; general characters and distribution 66; pectoral girdle 126; pelvic fins 132; teeth 110; skull 121 f.; spinal column 112 and 114

Garialidae _39_

_Garialis_ _39_, _212_

Garial 210

Gar pike 33; see _Lepidosteus_

_Gavialis_ _39_

_Gazella_ _46_

Gazelle _46_; skull 468

Geckonidae _37_; see Gecko

Gecko _37_; epipubis 293; parietals 277; supratemporal fossa 283; vertebrae 275

Gibbon _49_; ribs 493; skull 482

Gill-rays, dogfish 78; salmon 95

_Giraffa_ _46_

Giraffe _46_, _359_; cervical vertebrae 445; manus 507; pes 523; ulna 501

Giraffidae _46_; skull 469

Girdle bone, frog 156

Glenoid cavity 25; crocodile 263; dog 405; duck 322; frog 162; newt 146; turtle 232; --fossa, dog 394

Globe-fish _33_

_Globicephalus_ _45_; cervical vertebrae 354; manus 506; skull 463

Gluteal surface of ilium, dog 410

_Glyptodon_ _44_; carapace 419; cervical vertebrae 443; caudal vertebrae 453; manus 505; pelvis 513; pes 522; teeth 425; thoraco-lumbar vertebrae 447

Glyptodontidae _44_, _352_; skull 459; see also _Glyptodon_

Gnathostomata _31_, _59_

Golden mole _49_; see Chrysochloris

Goniopholidae _39_

_Goniopholis_ _39_; vertebrae 275

Goose 334; beak 329; Spur-winged--41

_Gorilla_ _49_; carpus 512; ribs 493; scapula 499; skull =483=; thoraco-lumbar vertebrae 450

Gruidae _41_; see Cranes

Gruiformes _41_

Guinea-pig _48_; tail 454

Gular shield, turtle 215

Gulls _42_, 335; aftershaft 328

Gymnodontidae _33_; beaks 111

Gymnophiona _35_; branchial arches 180; general characters 136; ribs 182; scales 168; skull 177; teeth 169; vertebrae 172

_Gymnura_ _49_; teeth 440; zygomatic arch 481

_Gypogeranus_ _41_; claws 330

_Gyrinophilus_ _35_; vertebral column 171

Haddock _33_

Hadrosauridae _39_

_Hadrosaurus_ _39_; skull 284

Hag or hag-fish _31_, 54 f.

Hair 3; dog 374; mammals 416

_Halicore_ _44_, _352_; manus 505; skull 460; teeth 425; see Dugong

Halicoridae _44_

Halitheriidae _44_

_Halitherium_ _44_, 352; femur 518; pelvis 514; teeth 425

Hallux 26; dog 415; duck 327; frog 167

Hamular process, dog 397

Hand, crocodile 266; dog 408 f.; duck 324; frog 165; newt 147; turtle 233

_Hapale_ _49_

Hapalidae _49_, 372 f.; teeth 441

Hare _48_, 366; acetabular bone 515; dental formula 435; femur 520; humerus 502; pelvis 515; scapula 497; skull 476; tail 454; thoraco-lumbar vertebrae 449; Cape jumping --, _47_; see _Pedetes_

_Harpagus_, _41_; serrated beak, 334

_Harriotta_, _32_, _66_

_Hatteria_, _37_, _197_; see _Sphenodon_

Haversian canals, 10; -- system, 10

Hawks, beak of, 330

Hedgehog, _49_, _370_; auditory ossicles, 488; humerus, 503; presternum, 490; skull, 480; spines, 417; see _Erinaceus_

Hemichordata, _30_, _50_

_Heptanchus_, _31_; branchial arches, 63, =120=; vertebrae, 114

Herbivorous dentition, 427, 430

Heron, _41_, 335; interorbital septum, 333; powder down feathers, 329

Herring, _33_

_Hesperornis_, _40_, _299_; caudal vertebrae, 333; clavicles, 338; teeth, 330; wing, 338

Heterocercal tail, 60, 116

Heterodont, 7

Heterostraci, _31_; general character, 54

_Hexanchus_, _31_; branchial arches, 63, 121

Hinge joint, 13

_Hipparion_, _46_; manus, 508; pes, =524=

Hippopotamidae, _45_

_Hippopotamus_, _45_, _359_; dental formula, 427; hair, 416; mandible, 467; manus, 506; pes, 523; scapula, 496; skull, 467; teeth, 345

Hoatzin, _41_; see _Opisthocomus_

Holocephali, _32_, 65, 104; clasper, 132; spinal column, 113; tail, 116; teeth, 109

Holoptychiidae, _33_

_Holoptychius_, _33_; scales, 105

Holostei, _33_; general characters, 68; teeth, 110; see Bony Ganoids

Hominidae, _49_, _373_

_Homo_, _49_; see Man

Homocercal tail, 60, 69, 117; codfish, 87

Homodont, defined, 7

Hoofs, 3, 418

Hoopoe, _42_, 335

_Hoplopterus_, spur, 330

Hornbill, _42_, 331; bony crest, 334; interorbital septum, 333

Horns, 3, 417

Horny plates on palate, 418; -- teeth, Lampreys, 4; Myxinoids, 57; _Ornithorhynchus_, 4

Horse, _46_, _360_; fibula, 519; malleus, 487; manus, 507; pes, =524=; skull, 471; teeth, 345, 430; ulna, 501

Howling monkey, _49_; see _Mycetes_

Humerals, duck, 303 f.

Humeral shield, turtle, 215

Humerus, 26; crocodile, 263; dog, 405; duck, 323; frog, 164; newt, 147; turtle, 232; wombat, =500=

Humming-birds, _42_, 335

Humpbacked whale, _44_, _357_

_Hyaena_, _48_, _369_; hallux, 526; pollex, 511; sacral vertebrae, 452; teeth, 437

Hyaenidae, _48_; humerus, 502

_Hyaenodon_, _48_, _368_

Hyaenodontidae, _48_

Hyaline cartilage, 10

_Hydrochaerus_, _48_; teeth, 437; see Capybara

_Hydromys_, _47_; dental formula, 436

Hydrophidae, _38_; scales, 270

_Hydropotes_, _46_; canines, 429

_Hyla_, _36_; fronto-parietal fontanelle, 179; sternum, 184

Hylidae, _36_

_Hylobates_, _49_; ribs, 493; skull, 482

Hyoid, 21; alligator, =285=; Amphibia, 180; birds, 336; cod, 100; crocodile, 259; dogfish, 77; dog, 399; duck, 320; frog, 161; newt, 144; reptiles, 284; salmon, 94; turtle, 231, =285=

Hyomandibular, 23; cod, 100; dogfish, 78; salmon, 94

_Hyomoschus_, _45_

Hyoplastron, turtle, 217

Hyostylic, 61, 119

_Hyotherium_, _45_; teeth, 427

_Hyperodapedon_, _37_, _198_; premaxillae, 284

_Hyperoödon_, _44_; skull, 464; sternum, 489; thoracic vertebrae, 448

Hypo-branchial, cod, 101; dogfish, 78

Hypo-hyal, cod, 100; salmon, 95

Hypo-ischium, Lacertilia, 292

Hypoplastron, turtle, 217

Hyporachis, 328

_Hypsilophodon_, _39_; predentary bone, 284

Hypsodont, defined, 345, 429

Hypural bone, cod, 85

Hyracidae, _47_

Hyracoidea, _47_; femur, 519; general characters, 362; manus, 510; nails, 418; skull, 472; teeth, 432

_Hyracotherium_, _46_; manus, 508; scapula, 496

_Hyrax_, _47_, _363_; see _Procavia_

Hystricidae, _47_

Hystricomorpha, _47_; auditory ossicles, 488

_Hystrix_, _47_; auditory ossicles, 488; see Porcupine

Ichthyodorulites, 106

Ichthyoidea, _35_; general characters, 134

Ichthyopsida, _31_; general characters, 59

Ichthyopterygium, 130

_Ichthyornis_, _40_; mandible, 335; pelvis, 341; teeth, 330; vertebrae, 332

Ichthyornithiformes, _40_, 300

Ichthyosauria, _37_; general characters, 195; ribs, 285

Ichthyosauridae, _37_

_Ichthyosaurus_, _37_, _197_; limbs, 290; palatines, 281; pectoral girdle, 288; position of limbs, 28; skull, =196=; teeth, 273; vertebral column, 275

Ichthyotomi, _31_; general characters, 62; fins, 130 f.; tail, 116

_Iguana_, _38_; teeth, 273

Iguanidae, _38_; zygosphenes, 200, 276

_Iguanodon_, _39_, 208 f.; jaws, 292; predentary, 284; sternum, 288; teeth, 272 f.; vertebrae, 275

Iguanodontidae, _39_

Iliac surface of ilium, dog, 410

Ilium, 25; crocodile, 266; dog, 409; duck, 325; frog, 165; mammals, 513 f.; newt, 149; reptiles, 291; turtle, 235

Incisors, dog, 376 f.; mammals, 344

Incus, dog, 393; man, dog and rabbit, =485=

Infra-marginal shield, turtle, 215

Infra-pharyngeal bone, cod, 101

_Inia_, _45_; cervical vertebrae, 444; lumbar vertebrae, 448

Innominate bone, dog, 409; mammals, 513

Insectivora, _48_; arm bones, 503; auditory ossicles, 488; cervical vertebrae, 446; general characters, 369 f.; manus, 512; pelvis, 515; pes, 527; sacrum, 452; shoulder-girdle, 499; skull, 480; sternum, 490; tail, 454; teeth, 440; thigh and shin, 520; thoraco-lumbar vertebrae, 450

Insectivora vera, _49_; general characters, 370

inter centra, 15; _Galeopithecus_, 370; Ichthyosauria, 195; Labyrinthodontia, 172; _Sphenodon_, 198; _Talpa_, 450

Interclavicle, 25; crocodile, 263; Monotremata, 494; reptiles, 289

Intercondylar notch, dog, 412

Intergular shield, turtle, 215

Interhyal, cod, 100

Intermedium, 27; see Carpus and Tarsus

Intermuscular bones, cod, 86

Internasal septum, dogfish, 76

Interorbital septum, birds, 333; crocodile, 247; duck, 317; reptiles, 277

Interspinous bones, cod, 86

Intertarsal ankle joint, 190

Intervertebral discs, 15, 378

Ischial tuberosity, dog, 411

Ischium, 25; crocodile, 266; dog, 410; duck, 325; frog, 165; newt, 149; turtle, 235

_Ischyodus_, _32_, _66_

Ivory, 5

Jacana, _42_; see _Parra_

_Jacare_, _39_; scutes, 271

Jaws, 21; cod, 98 f.; crocodile, 252 f.; dog, 395 f.; dogfish, 77; duck, 317 f.; frog, 158 f.; newt, 143 f.; salmon, 93 f.; turtle, 229 f.

Jerboa, _47_; cervical vertebrae, 446; pes, 526

Joints, kinds of, 13

Jugal, 22; crocodile, 255; dog, 398; duck, 318; turtle, 229

Jugulares, 132

Kangaroo, _43_; dental formula, 423; lumbar vertebrae, 447; pectineal process, 513; pes, 522; tail, 453; teeth, 345

Kestrel, claws, 330

Killer, _45_; see _Orca_

Kiwi, _40_; see _Apteryx_

Knee-cap, see patella

Koala, _43_; lumbar vertebrae, 447; pes, 522; tail, 453

Kükenthal, W., on teeth of Cetacea, 426; on teeth of Marsupials, 422

Labial cartilage, dogfish, 77; _Squatina_, 119

Labridae, _33_

_Labrus_, _33_; see Wrasse

Labyrinthodontia, _35_; buckler, 168; general characters, 135; interparietal foramen, 173; pelvis, 187; ribs, 182; skull, 176; teeth, 169

Lacertilia, _37_; general characters, 199; pectoral girdle, 288; skull, 277; vertebrae, 275

Lachrymal, 20; cod, 97; crocodile, 251; dog, 394; duck, 317; salmon, 93

Lacunae, 10

_Lagenorhynchus_, _45_; skull, 462

_Lagostomus_, _47_; maxillae, 477

Lambdoidal crest, duck, 315

Lamella of malleus, dog, 393

Lamnidae, _32_

Lamprey, _31_, 55 f.

Lancelet, _30_; see _Amphioxus_

Laridae, _42_; see Gulls

Larks, _42_

Larvacea, _30_; notochord, 51

_Latax_, _48_; pes, 526

Lateral ethmoid, 21; cod, 97; salmon, 89 f.

Leathery turtle, _37_; see _Dermochelys_

Lemuroidea, _49_; caudal vertebrae, 454; general characters, 372; nails, 418; ribs, 493; sacrum, 452; skull, 482; thoraco-lumbar vertebrae, 450; see Lemurs

Lemurs, carpus, 512; pes, 527; teeth, 441; see Lemuroidea

Lenticular, 485; dog, 393

_Lepidosiren_, _34_, _70_; branchial arches, 125; fins, 130

Lepidosteidae, _33_

_Lepidosteus_, _33_; attachment of teeth, 108; distribution, 66; pectoral fins, 131; scales, 67, 104; skull, 123; tail, 117; vertebrae, 68

_Lepidotus_, _33_; teeth, 110

Leporidae, _48_

Lepospondyli, _35_

_Lepus_, _48_; see Hare

_Leptoptilus_, _41_; see Adjutant

_Lialis_, _37_, 289

Limbs, general account, 26; modifications in position of, 28; reptiles, 289

Llama, _45_, 359; cervical vertebrae, 445; skeleton, =496=; teeth, 428

Limicolae, _42_

Lingual apparatus, lampreys, 58; myxinoids, 57

Lion, _48_

_Loemanctus longipes_, shoulder girdle and sternum, =287=

Loggerhead turtle, carapace, =216=

_Lophiodon_, _46_; teeth, 345, 429

Lophiodontidae, _46_

Lophiomyidae, _47_

_Lophiomys_, _47_; pes, 526; skull, 476

_Lophius_, attachment of teeth, 107

Lower jaw, see Mandible

Lumbar vertebrae, 16; crocodile, 242; dog, 378 f.; duck, 311

Lunar, 27; dog, 408

_Macacus_, _49_; cervical vertebrae, 446

_Machaerodus_, _48_; upper canines, 437

_Macrauchenia_, _46_, 358; calcaneum, 360; cervical vertebrae, 445; fibula, 519; tarsus, 523; ulna, 501

Macraucheniidae, _46_, 509

Macropodidae, _43_, _350_; dental formula, 423; pes, 522

_Macropus_, _43_; see Kangaroo

Macroscelidae, _49_

_Macroscelides_, _49_; skull, 480

Magnum, 27; see Carpus

Malar, 22; see jugal

Malleus, dog, 393; man, dog and rabbit, =485=

Mammalia, _42_; auditory ossicles, 485; cervical vertebrae, 442; exoskeleton, 416; general characters, 343; manus, 503; Mesozoic --, 348; pectoral girdle, 493; pelvic girdle, 512; pes, 521; ribs, 490; sacral and caudal vertebrae, 451; skull, 455; sternum, 489; thigh and shin, 517; thoraco-lumbar vertebrae, 447

Man, _49_; arm bones, 503; auditory ossicles, 488; caudal vertebrae, 454; cervical vertebrae 446; pelvis, 515; pes, 527; ribs, 493; scapula, 499; skull, 483; sternum, 490; teeth, 441

Manatee, _44_; see _Manatus_

Manatidae, _44_

_Manatus_, _44_; cervical vertebrae, 444; dental formula, 425; humerus, 501; manus, 505; pelvis, 514; skull, 460; sternum, 489; teeth, 345; thoraco-lumbar vertebrae, 448

Mandible, birds, 335; cod, 100; crocodile, 258; dog, 398; duck, 319; frog, 160; Hippopotamus, =467=; Isabelline bear, =438=; newt, 144; salmon, 94; turtle, 230

Manidae, _44_; see _Manis_

_Manis_, _44_; auditory ossicles, 487; manus, 504; scales, 3, 417; skull, 459; _M. macrura_ xiphisternum, 489; see Pangolin

Manubrium of malleus 486; dog, 393; -- sterni, dog 404

Manus, 26; crocodile, 265; dog, 408, =413=; duck, 323; frog, 164; mammalia, 503; newt, 147; Perissodactyles, =508=; turtle, 233

Marginal plate, turtle 216; -- ray, 131; -- shield, turtle, 214

Marmoset, _49_, 372 f.

Marmot, frontals, 476

Marsipobranchii, _31_, _53_; spinal column, 56

Marsupial bones, 513

Marsupial mole, 43; see _Notoryctes_

Marsupialia, _43_; arm bones, 499; auditory ossicles, 486; cervical vertebrae, 443; caudal vertebrae, 453; general characters, 349; manus, 504; pectoral girdle, 494; pelvis, 513; pes, 521; ribs, 491; sacral vertebrae, 451; skull, 456; teeth, 422; thigh and shin, 517; thoraco-lumbar vertebrae, 447

_Mastodon_, _47_, _365_; teeth, 434

_Mastodonsaurus_, _35_, _136_; pelvis, 187

Mastoid portion of periotic, dog, 391

Maxilla, 22; cod, 98; crocodile, 254; dog, 397; duck, 318; frog, 159; newt, 144; turtle, 229

Maxillo-mandibular arch, 21

Maxillo-palatine, duck, 318

Maxillo-turbinal, dog, 395

Meatus, external auditory --, crocodile, 250; dog, 393; turtle, 228; internal auditory --, crocodile, 251; dog, 392, 400; turtle, 228

Meckel's cartilage, 22; cod, 100; dogfish, 77; salmon, 94

Median ethmoid, 21; cod, 98; Gymnophiona, 179; salmon, 91; -- fin, Amphibia, 52; cod, 86; dogfish, 79

Megachiroptera, _49_; general characters, 371

_Megalobatrachus_, _35_, _135_; carpus, 186; skull, 175

Megalosauridae, _38_

_Megalosaurus_, _38_, _208_

_Megapodius_, spur, 330

_Megaptera_, _44_, _357_

Megatheriidae, _44_, 352; humerus, 501; leg bones, 517; pelvis, 513; sacrum, 452; teeth, 424; thoraco-lumbar vertebrae, 447

_Megatherium_, _44_; femur, 517; manus, 505; pectoral girdle, 495; pes, 522; skull, 458

Megistanes, _40_, _299_

Membranous cranium, 17

Menobranchidae, _35_

_Menobranchus_, _35_, _135_; carpus, 185; pes, 188; skull, 174; teeth, 169

_Menopoma_, _35_; see _Cryptobranchus_

Mento-meckelian, 22; frog, 161; reptiles, 284

Merganser, _41_; beak, 329

_Mergus_, _41_

Merrythought, duck, 322

Mesethmoid, 20; dog, 390; duck, 317

_Mesoplodon_, _44_; teeth, 427

Mesopterygium, 79

Mesosauridae, _37_

_Mesosaurus_, _37_

Mesosternum, dog, 404

Metacarpal quill, duck, 303

Metacarpo-digital, duck, 303

Metacarpus, 26; see Manus

Metacromion, hares and rabbits, 497

Meta-pterygium, 79

Metatarsus 26; see Pes

Metatheria, _43_; general characters, 349

_Metriorhynchus_, _39_, 278

Microchiroptera, _49_; general characters, 371

_Microgale_, _49_; caudal vertebrae, 454

Mid-digital quill, duck, 303

Milk-teeth, 344; dog, 377; horse, 430

Moa, _40_, _299_; aftershaft, 328; pectoral girdle, 336; wing, 338

Molar teeth, 344; dog, 376 f.

Mole, _49_, _370_; auditory ossicles, 488; cervical vertebrae, 446; humerus, 503; manus, 512; presternum, 490; shoulder girdle, 499; skull, 481; teeth, 440; Golden --, _49_; see _Chrysochloris_; Marsupial --, _43_; see _Notoryctes_

_Molge_, _35_, _135_; see Newt

Monitor, _38_; see _Varanus_

Monkey, _49_, _373_; see under Primates

Monodelphia, _43_; characters of, 351

_Monodon_, _45_, _357_; see Narwhal

Monophyodont, defined, 7, 344

Monopneumona, _34_

Monotremata, _42_; arm bones, 499; auditory ossicles, 486; caudal vertebrae, 453; cervical vertebrae, 443; general characters, 346; manus, 504; pectoral girdle, 493; pelvis, 513; pes, 521; ribs, 490; sacral vertebrae, 451; skull, 455; sternum, 489; teeth, 422; thigh and shin, 517; thoraco-lumbar vertebrae, 447

_Morosaurus_, _38_, _207_; pes, 294

_Mosasaurus_, _38_, _204_

_Moschus_, _46_; canines, 429

Mouse, _47_; teeth, 437; see _Mus_

Mud-fish, _34_

Multituberculata, _43_, _348_

Muntjac, _46_; see _Cervulus_

Muraenidae, _33_

Muridae _47_

_Mus_, _47_; _M. musculus_, teeth, 437; _M. sylvaticus_, sternum and shoulder girdle, 498

Musk deer, _46_; canines, 429

Mustelidae, _48_; teeth 439

_Mycetes_, 49; hyoid, 485; mandible, 484; skull, 482

Myliobatidae, _32_; teeth, 109

Myomorpha, _47_

_Myrmecobius_, teeth, 423

_Myrmecophaga_, _44_; manus 505; pectoral girdle, 495; skull, 458

Myrmecophagidae, _44_, 424; see Anteaters

Mystacoceti, _44_; general characters, 356; hind limb, 518; manus, 505; pectoral girdle, 495; skull, 461; teeth, 426

_Myxine_, _31_, 55; fins, 115; notochordal sheath, 9

Myxinoidei, _31_, 55

Nails, 3; Amphibia, 168; mammals, 417

Nares: anterior --, crocodile, 252, 257; dog, 401; duck, 317; newt, 143; turtle, 225, 229; posterior --, crocodile, 257; dog, 402; duck, 318; frog, 158; newt, 143; turtle, 230

Narial cavity, salmon, 89; -- passage, crocodile, 254; dog, 395; -- septum, dog, 401

Narwhal, _45_, _357_; teeth, 427

Nasal 21; crocodile, 252; dog, 394; duck, 317; frog, 158; newt, 143; turtle, 228; -- capsule, 20; cod, 97; crocodile, 252; dog, 394; dogfish, 74; frog, 158; newt, 143; turtle, 228; -- cavity, dog, 388; -- fossae, salmon, 89; -- horns, rhinoceros, 3

Navicular, 27; dog, 414

Neornithes, _40_; general characters, 298

_Nesodon_, _46_, _361_; pes, 525; teeth, 432

Nesodontidae, _46_

Neural arch, 14; -- plate, turtle, 215; -- spine, 14

Neuromere, defined, 112

Newt, _35_; anterior limb, 147; hyoid apparatus or visceral arches, 144, =181=; pelvic girdle, 149; ribs, 145; shoulder girdle, =146=; skull, 140; sternum, 145; vertebral column, 138

Notidanidae, _31_; calcification of vertebrae, 114; pectoral fins, 130; vertebral column, 113; visceral arches, 63, 119 f.

Notochord, _Amphioxus_ 52; Balanoglossus, 50; dogfish, 72; Tunicates, 51

_Nothosaurus_, _37_, _193_; supratemporal fossae, 283

Nothosauridae, _37_

_Notoryctes_, _43_; arm bones, 500; caudal vertebrae, 453; cervical vertebrae, 443; claws, 418; dental formula, 423; manus, 504; pelvis, 513; pectoral girdle, 494; pes, 521; ribs, 491; sacrum, 452; skull, 457; sternum, 489; thigh and shin, 517

Notoryctidae, _43_, _350_

Nuchal plate, turtle, 215; -- shield, crocodile, 238; turtle, 214

_Nyrania_, _35_; palatines, 177

Occipital condyle, crocodile, 246; dog, 386; duck, 315; frog, 154; turtle, 224; -- crest, dog, 386; -- segment, crocodile, 246; dog, 384; turtle, 224

_Odontaspis_, _32_; succession of teeth, =107=

Odontoblast, 7

Odontoceti, _44_; general characters, 357; manus, 505; pectoral girdle, 495; skull, 462; sternum, 489; teeth, 426

Odontolcae, _40_; general characters, 299

_Odontopteryx_, _40_; jaws, 334

_Ogmorhinus_, _48_; mandibular ramus, =439=

Olecranon process, dog, 406; duck, 323; frog, 164

Olfactory capsule, see nasal capsule; -- cavity, dog, 388; -- chamber, dog, 395; -- fossa, dog, 390

Olm, _35_

_Omosaurus_, exoskeleton, 272

Omosternum, frog, 163

_Onychodactylus_, _35_; nails, 168

Operculum, cod, 101; salmon, 95

Ophidia, _38_; general characters, 202; jaw bones, 280; scales, 270; skull, 277 f.; vertebral column, 275

_Ophisaurus_, _38_; limbs, 289; pectoral girdle, 289

Opisthocoelous, defined, 14

_Opisthocomus_, 41; skull, 334

Opisthotic, 20; cod, 96; crocodile, 250; salmon, 89 f.; turtle, 227

Opossum, _43_; caudal vertebrae, 453; teeth, 423

Optic capsule, 20; crocodile, 251; dog, 394; turtle, 228

Orang, _49_; carpus, 512; ribs, 493; thoraco-lumbar vertebrae, 450

Orbit, crocodile, 257; dogfish, 74; duck, 317

Orbital ring, cod, 97; salmon, 93

Orbitosphenoid, 19; dog, 388; duck, 317; newt, 141

_Orca_, _45_; teeth, 427

_Oreodon_, _45_; see _Cotylops_

Ornithodelphia, _42_; general characters, 346

Ornithosauria, _212_

Ornithorhynchidae, _43_

_Ornithorhynchus_, _43_; beak, 3, 418; caudal vertebrae, 453; manus, 504; pelvis, 513; sacral vertebrae, 451; shoulder girdle, =347=; skull, 455; spur, 418; tarsus, 27 n.; teeth, 4, 346, 422; thoraco-lumbar vertebrae, 447

Ornithopoda, _39_; general characters, 209

Orthopoda, _39_; general characters, 208; pubes, 292

Orycteropodidae, _44_; teeth 425

_Orycteropus_, _44_; hair, 416; manus, 505; pectoral girdle, 495; pelvis, 513; skull, 459; see Aard Vark

Osborn, H.F., on Mesozoic Mammals, 348

Os entoglossum, duck, 320

Osteoblast, 11

Osteoclast, 11

Osteodentine, 108

Osteostraci, _31_; general characters, 54

_Ostracion_, _33_, 69; plates, 105

Ostracionidae, _33_

Ostracodermi, _31_; general characters, 54

Ostrich, _40_, _299_; aftershaft, 329; cervical vertebrae, =331=; claws, 330; foot, 342; manus, 338; pelvic girdle and sacrum, =340=; pubis, 341; tibio-tarsus, 341; wing, =339=

_Otaria_, _48_; dentition, 439; tympanic bulla, 480

Otariidae, _48_, _369_; auditory ossicles, 488; scapula, 498; skull, 480

Owen's apteryx, pelvic girdle and sacrum, =340=

Owen's chameleon, epidermal horns, 271

Owls, _42_, 335; aftershaft, 329; foot, 342

Owl-parrot, _42_; see _Stringops_

Ox, _46_, 359; atlas and axis, =445=; three cervical vertebrae, =15=; femur, =518=; manus, 507; teeth, 345; two thoracic vertebrae, =449=

Paca, _48_

Paired fins, 127

Palaeoniscidae, _32_

_Palaeoniscus_, _32_; scales, 67

Palaeospondylidae, _31_

_Palaeospondylus_, _31_, 58

_Palaeosyops_, _46_; teeth, 432

Palaeotheriidae, _46_

_Palaeotherium_, 46; skull, 471; teeth, 430

_Palamedea_, _41_; spur, 330, 338

Palamedeae, _41_

Palate, reptiles, 280 f.

Palatine, cod, 98; crocodile, 254; dog, 397; duck, 318; frog, 160; salmon, 93; turtle, 230

Palato-pterygo-quadrate bar, 22; dogfish, 77; fish, 120 f.; salmon, 93

Palm civet, _48_

Pangolin, _44_; pectoral girdle, 495; pelvis, 513; caudal vertebrae, 453; see _Manis_

Parachordals, 17

_Paradoxurus_, _48_; tail, 454

Parasphenoid, 21; cod, 97; frog, 156; newt, 141; reptiles, 278; salmon, 93

Parasuchia, _39_; general characters, 211

Parethmoid, 21 n.

Pariasauria, _36_

_Pariasaurus_, _36_, _192_; pectoral girdle, 289; pelvis, 292; supratemporal fossa, 283; teeth, 273

Parietal, 19; cod, 96; crocodile, 247; dog, 386; duck, 314; newt, 141; salmon, 91; turtle, 225; -- segment, crocodile, 247; dog, 386; turtle, 225

Paroccipital process, dog, 386

_Parra_, _42_; spur, 330

Parrots, 335; aftershaft, 328; beak, 330; epiphyses of centra, 332; foot, 342; powder-down feathers, 329; skull, 334

Parrot fish, _33_; see _Scarus_

Passeres, aftershaft, 328

Passeriformes, _42_

Patella, dog, 412; duck, 327

_Pavo_, _41_; _P. cristatus_, shoulder girdle and sternum, =337=

Peacock, _41_; see _Pavo_

Peccary, pes, 523

Pecora, _46_, _359_; teeth, 429

Pectinated incisors, _Galeopithecus_, 370, 440; _Procavia_, 362

Pectineal process, duck, 326

Pectoral fins, cod, 103; dogfish, 79; -- girdle, 24; Amphibia, 184; birds, 336; cod, 101; crocodile, 262; dog, 404; dogfish, 79; duck, 321; fish, 126; frog, 162; mammalia, 493; newt, 145; reptiles, 288; turtle, 231; -- shield, turtle, 215

_Pedetes_, _47_; manus, 511; tail, 454

Pelican, _41_, 335; clavicles, 338

_Pelicanus_, _41_; _P. conspicillatus_ shoulder girdle and sternum, =337=

_Pelobates_, _36_; vertebrae, 172; _P. cultripes_ teeth, 169

Pelobatidae, _36_

Pelvic fins, cod, 103; dogfish, 82; fish, 131; -- girdle, 25; Amphibia, 187; birds, 339; crocodile, 266; dog, 409; dogfish, 81; duck, 324; fish, 127; frog, 165; mammals, 512; newt, 149; Ratitae, =340=; Reptilia, 291; turtle, 235

Penguin, _40_; distribution of feathers, 328; fibula, 341; foot, 342; manus, 338; metatarsus, 342; pneumaticity of skeleton, 331; skull, 333; sternum, 336; thoracic vertebrae, 332; wing, 329, =339=

Penna, duck, 303

Pentedactylate, defined, 26

_Perameles_, _43_; atlas, 443; pectoral girdle, 494

Peramelidae, _43_, _350_; auditory ossicles, 486; pes, 522

_Perca_, _34_

Perch, _34_; pelvic fin, 132; urostyle, 117

Percidae, _34_

Perennibranchiata, _35_; characters, 135

Perichondrium, 10

Perichordal sheath, 16

Periosteal ossification, 10

Periosteum, 10

Periotic, dog, 390; -- capsule, see Auditory capsule

Perissodactyla, _46_; cervical vertebrae, 445; general characters, 359; manus, 507; pes, 523; ribs, 491; scapula, 496; skull, 470; teeth, 429; thoraco-lumbar vertebrae, 448

Persistent pulps, 5

Pes, 26; crocodile, 268; dog, =413=, 414; duck, 327; frog, 166; mammals, 521; reptiles, 293; turtle, 236; of Tapir, Rhinoceros, _Hipparion_ and Horse, =524=

_Petromyzon_, _31_, 55 f.; notochordal sheath, 9

Petromyzontidae, _31_, 55

Petrous portion of periotic, dog, 391

_Pezophaps_, _42_; see Solitaire

_Phacochaerus_, _45_; teeth, 428

_Phaëthon_, _41_; metatarsals, 342

_Phalacrocorax_, _41_

Phalangeridae, _43_, 350

Phalanges, 26; see Manus and Pes

Phaneroglossa, _36_

Pharyngo-branchial, cod, 101; dogfish, 78; salmon, 95

Pharyngognathi, _33_

_Phascolarctus_, _43_; see Koala

Phascolomyidae, _43_, _350_

_Phascolomys_, _43_, 349; see Wombat

_Phascolotherium_, _43_, 348

Phenacodontidae, _47_

_Phenacodus_, _47_, _362_; caudal vertebrae, 454; manus, =510=; pes, 525; scapula, 497; skull, 472; thoraco-lumbar vertebrae, 449

_Phocaena_, _45_, _357_; skull, 462; thoraco-lumbar vertebrae, 448; _P. phocaenoides_, ossicles, 420

Phocidae, _48_, _369_; scapula, 497; tympanic bulla, 480

_Phoronis_, _30_, 50 f.

_Phororhacos_, _41_; anterior nares, 333; ischia, 341

_Physeter_, _44_; cervical vertebrae, 444; manus, 505; skull, 464; teeth, 426

Physeteridae, _44_; ribs, 491; thoraco-lumbar vertebrae, 448

_Physodon_, _44_; teeth, 426

Physodontidae, _44_

Physostomi, _33_

Phytosauridae, _39_

_Phytosaurus_, _39_; see _Belodon_

Pici, _42_

_Picus_, _42_; see Woodpecker

Pig, _45_, _359_; skull, 465 f., =466=; teeth, 345, 427

Pigeons, _42_, 334 f.; aftershaft, 329; pneumaticity of skeleton, 331

Pike, _33_; pelvic fin, 132; teeth, 107, 110

Pinnipedia, _48_; arm bones, 502; auditory ossicles, 488; general characters, 369; manus, 511; pelvis, 515; pes, 526; skull, 480; teeth, 439; thigh and shin, 520; thoraco-lumbar vertebrae, 450

_Pipa_, _36_; hyoid apparatus, 182; jaws, 169; skull, 180; sternum, 184; vertebrae, 172

Pipidae, _36_

Pisces, _31_; general characters, 60

Piscivorous dentition, 426, 440

Pisiform, 345, 504; crocodile, 265; dog, 408; turtle, 233

Pituitary fossa, crocodile, 247; -- space, 17

Placodontia, _36_

_Placodus_, _36_, _192_; teeth 273

Placoid scale, 4, 60, 104

Plantigrade, defined, 358 n.

Plastron, _Dermochelys_, 272; _Chelone midas_, 217, =218=, 271

Platanistidae, _45_

_Platanista_, _45_; cervical vertebrae, 444; skull, 464

Plectognathi, _33_; vertebrae, 115

_Plectropterus_, _41_; _P. gambensis_, spur, 330

Plesiosauridae, _37_; limbs, 193; parasphenoid, 192; skull, 278

_Plesiosaurus_, _37_, _193_; position of limbs, 28

Pleuracanthidae, _63_; fins, 115

Pleurodira, _37_; general characters, 195

Pleurodont, 159, 199, 273

Pleuronectidae, _33_

Pleuropterygii, _31_, 63

_Pliosaurus_, _37_, _193_

Plovers, _42_, 334; thoracic vertebrae, 332

Pneumaticity of bird's skeleton, 331

_Polacanthus_, _39_; exoskeleton, 272

Pollex, 26; see Manus

_Polyodon_, _32_, 104; distribution, 66; pectoral fins, 131; skull, 122; spinal column, 112; teeth, 110

Polyodontidae, _32_

_Polyonax_, _39_, _209_; beak, 271; frontals, 277; jaw, 274; predentary, 284

Polyprotodont, 423

Polyprotodontia, _43_; general characters, 350

Polypteridae, _33_

_Polypterus_, _33_, _68_; distribution, 66; exoskeleton, 67; pectoral fins, 131; pelvic fins, 132; pelvis, 127; scales, 104; skull, 122; tail, 116

_Pontoporia_, _45_; cervical vertebrae, 444; teeth, 426

Porcupine, _47_; pes, 526; skull, 476, =477=; spines, 417

Porpoise, _45_, _357_; thoraco-lumbar vertebrae, 448

Postaxial, 28

Posterior cornu, duck, 320; turtle, 231; -- limb, 26; Amphibia, 188; birds, 341; dog, 412; duck, 326; frog, 166; newt, 149, =148=; reptiles, 293; turtle, 235, =234=

Postfrontal, 21; crocodile, 250; turtle, 225

Postorbital bar, crocodile, 250, 255 f.; _Hatteria_, 283; -- groove, dogfish, 76

Post-temporal, cod, 102; reptiles, 283; -- bar, crocodile, 256; _Hatteria_, 283

_Potamogale_, _49_, 367, 370; shoulder girdle, 499; teeth, 440

Potamogalidae, _49_

Powder-down feathers, 329

Pre-axial, 28

Precoracoid, 25; frog, 163; newt, 147; reptiles, 288; turtle, 232

Predentary, reptiles, 284

Predigital quill, duck, 303

Prefrontal, 21; crocodile, 249; reptiles, 278; turtle, 225

Prefronto-lachrymal, newt, 141

Prehallux, frog, 167 f.

Premaxilla, 22; cod, 98; crocodile, 252; dog, 398; duck, 314, 318; frog, 158; newt, 143; salmon, 94; turtle, 230

Premolar, dog, 370, 377; mammals, 344

Prenasal process, frog, 158

Pre-orbital vacuity, reptiles, 283

Presphenoid, 19; dog, 388

Prespiracular ligament, dogfish, 77

Presternum, dog, 404

Primaries, duck, 303

Primates, _49_; arm bones, 503; auditory ossicles, 488; cervical vertebrae, 446; general characters, 372; manus, 512; pelvis, 515; pes, 527; ribs, 493; sacrum, 452; shoulder girdle, 499; skull, 482 f.; sternum, 490; tail, 454; teeth, 441; thigh and shin, 520; thoraco-lumbar vertebrae, 450

_Priodon_, _44_; caudal vertebrae, 453; manus, 505; stapes, 487; sternum, 489; teeth, 424

Pristidae, _32_

_Pristis_, _32_; snout or rostrum, 109, 119

Proboscidea, _47_; arm bones, 502; cervical vertebrae, 445; general characters, 364; femur, 519; manus, 511; pelvis, 514; pes, 526; scapula, 497; skull, 473; teeth, 433; thoraco-lumbar vertebrae, 449

_Procavia_, _47_, _363_; auditory ossicles, 487; caudal vertebrae, 453; dental formula, 432; humerus, 502; manus, 510; pelvis, 514; pes, 525; ribs, 491; scapula, 497; skull, 433, 472; tarsus, 27; thoraco-lumbar vertebrae, 449

Process, alinasal --, frog, 158; basi-pterygoid --, birds, 334; coracoid --, dog, 405; coronoid -- (of mandible), dog, 398; duck, 319; coronoid -- (of ulna), dog, 408; pectineal --, duck, 326; postfrontal --, duck, 316; postglenoid --, dog, 394; postorbital -- (of frontal), dog, 388; postorbital -- (of jugal), dog, 398; posterior articular --, duck, 319; zygomatic --, dog, 394

Processus brevis, 486; -- gracilis, 486; -- longus, 486; dog, 393

Procoelous, defined, 14

_Prodelphinus_, _45_; skull, 462

Proganosauria, _37_

Prone position, 29

Prongbuck, _46_; horns, 417

Pro-otic, 20; frog, 157; turtle, 227

Pro-pterygium, dogfish, 79

Proteidae, _35_

_Proteles_, _48_; teeth, 437

Protelidae, _48_

Proterosauridae, _37_

_Proterosaurus_, _37_; teeth, 198, 274; vertebrae, 197

_Proteus_, _35_, 135, 182; branchial arches, 180; digits, 187; pes, 188; skull, 174

_Protopterus_, _34_, _70_, 117; branchial arches, 121, 124; fins, 130; skull, 124; vestigial gill on pectoral girdle, 129

Prototheria, _42_; general characters, 346

Proximal, defined, 23 n.

_Psephurus_, distribution, 66

_Pseudopus_, _38_; limbs, 289

Psittaci, _42_; see Parrots

_Pteranodon_, _39_, _274_; pectoral girdle, 289

Pteranodontidae, _39_

_Pteraspis_, _31_, _54_

_Pterichthys_, _31_, _55_

_Pterocles_, _42_; see Sandgrouse

Pteroclidae, _42_

Pterodactylidae, _39_

_Pterodactylus_, _39_, 213

Pteropidae, _49_; skull, 481

_Pteropus_, _49_; dental formula, 441; tail, 454

Pterosauria, _39_; general characters, 212; ischia, 292; limbs, 291; pre-orbital vacuity, 284; ribs, 285; sternum, 287; vertebrae, 275 f.

Pterotic, 20; cod, 96; salmon, 90 f.

Pterygoid, cod, 98; crocodile, 255; dog, 397; duck, 318; frog, 160; newt, 144; salmon, 93; turtle, 230; -- fossa, crocodile, 255; -- plate, dog, 388

Pterylae, 328

Pubis, 25; crocodile, 266 f.; duck, 325; dog, 411; frog, 165; newt, 149; reptiles, 292; turtle, 235

Pygal plate, turtle, 217; -- shield, turtle, 214

Pygopodidae, _37_

Pygostyle, duck, 307, 312

_Python_, _38_; ischio-pubis, 292; jaws, 280; vestiges of limbs, 289, 293

Pythonomorpha, _38_; general characters, 204; limbs, 290; teeth, 273

Quadrate, 22; cod, 98; crocodile, 255; duck, 319; frog, 160; newt, 144; salmon, 93; turtle, 229

Quadratojugal, 22; crocodile, 255; duck, 318; frog, 160; turtle, 229

Quill, duck, 302

Rabbit, _48_, 366; pollex, 511

Raccoon, 369

Rachis, duck, 302

Rachitomous, defined, 171

Radiale, 27; see Carpus

Radialia, 115; dogfish, 79 f.

Radio-ulna, frog, 164

Radius, 26; crocodile, 265; dog, 406; duck, 323; newt, 147; turtle, 233

_Raia_, _32_; calcification of vertebrae, 114

Raiidae, _32_

_Rana_, _36_; see Frog

Ranidae, _36_; shoulder girdle, 185

Rat, pes, 526

Ratitae, 40; caudal vertebrae, 333; clavicles, 338; foot, 342; general characters, 298; skull, 333; sternum, 336; vomers, 334; wing, 338

Rattlesnake, _38_; rattle, 3, 270

Ray, pectoral fin, 130; Eagle --, Electric -- and Sting --, _32_

Rectrices, 303, 329

Reed-fish, _33_

Reindeer, antlers, 469

Remicle, duck, 304

Remiges, 303, 329

Reptiles, anterior limb, 290; exoskeleton, 270; fossae in skull, 281; pectoral girdle, 288; pelvic girdle, 291; posterior limb, 293; ribs, 285; skull, 276; sternum, 287; teeth, 272; vertebral column, 275

Reptilia, _36_; general characters, 190; see Reptiles

_Rhabdopleura_, _30_, 50

_Rhamphastos_, _42_; see Toucan

Rhamphorhynchidae, _39_

_Rhamphorhynchus_, _39_, 213, 274

_Rhea_, _40_; aftershaft, 329; claws, 330; ischia, 341; manus, 338; _R. macrorhyncha_, pelvic girdle and sacrum, =340=

Rheornithes, _40_

_Rhina_, _32_; see _Squatina_

Rhinal process, frog, 158

_Rhinoceros_, _46_, 360, 419; femur, =518=; fibula, 519; malleus, 487; manus, 508; nasal horns, 3, 417; pes, 525; skull, =421=, 470; teeth, 430; ulna, 501; _R. antiquitatis_, 470

Rhinocerotidae, _46_

Rhinolophidae, _49_

Rhiptoglossa, _38_

Rhizodontidae, _33_

_Rhizodus_, _33_; teeth, 110

Rhynchocephalia, _37_; general characters, 197; humerus, 290; teeth, 273 f.; vertebrae, 275

Rhynchosauridae, _37_; maxillae, 198

_Rhytina_, _44_, 352, 425; humerus, 501; skull, =460=

Rhytinidae, _44_

Ribs, 23; Amphibia, 182; birds, 336; cod, 86; crocodile, 259; dog, 402; dogfish, 73; duck, 320; fish, 125; frog, 153; mammalia, 490; newt, 145; reptiles, 285

Ridge, supra-orbital and suborbital, dogfish, 74

Rodentia, _47_; auditory ossicles, 488; cervical vertebrae, 446; dental formula, 435; general characters, 365; pelvis, 515; pes, 526; humerus, 502; manus, 511; ribs, 493; sacrum, 452; shoulder girdle, 497; skull, 476; sternum, 489; tail, 454; teeth, 421; thigh and shin, 520; thoraco-lumbar vertebrae, 449

Roller, _42_, 335

Rooted teeth, defined, 5

Rorqual, _44_, 357; cervical vertebrae, 444

Rostrum, crocodile, 247; dogfish, 74; duck, 316; _Pristis_, 119; -- of sternum, duck, 321

Röse, C., on teeth of Marsupials, 422

Ruminantia, _46_, _359_; auditory ossicles, 487; fibula, 519; horny plates on palate, 418; hyoid, 470; manus, 507; odontoid process, 445; pes, 523; scapula, 495; teeth, 420, 429

Sabre-toothed lion, _48_; see _Machaerodus_

Sacral ribs, crocodile, 243; -- surface of ilium, dog, 409; -- vertebrae, 16; crocodile, 243; dog, 383; duck, 312; frog, 153; newt, 140; turtle, 222

Sacrum, duck, 310; see Sacral vertebrae

Sagittal crest, dog, 386

_Saiga_, skull, 468

Salamander, _35_

_Salamandra_, _35_, _135_; antibrachium and manus of larva, =186=; manus of larva, 185; tarsus, 27

Salamandrina, _35_, _135_; skull, 175; sternum, 182

_Salmo_, _33_

Salmon, _33_; branchial arches, 95; chondrocranium, 87; opercular bones, 95; pectoral fins, 131; skull, 87

Salmonidae, _33_

Sandgrouse, _42_, 335

_Sarcophilus_, _43_; teeth, 423

Sauropoda, _38_; general characters, 205; teeth, 273; vertebrae, 276

Sauropsida, _36_; general characters, 189

Sauropterygia, _37_; general characters, 192; limbs, 290; palate, 281; pectoral girdle, 288; vertebrae, 276

Saw-fish, _32_; see _Pristis_

Scales, cod, 83; crocodile, 237; ctenoid, 8; cycloid, 8; duck, 302; ganoid, 8; Gymnophiona, 168; mammals, 417

Scale-foot, 37

Scalpriform, 366

_Scaphirhynchus_, _32_, _104_; distribution, 66; exoskeleton, 67; spinal column, 112

Scaphoid, 27; mammals, 504 f.

Scapho-lunar, dog, 408

Scapula, 25; cod, 103; crocodile, 263; dog, 404; duck, 322; frog, 162; newt, 146; turtle, 232

Scapular shield, armadillo, 419

Scapus, duck, 302

_Scarus_, _33_; beaks, 111

Scelidosauridae, _39_

Schizognathous, defined, 335

Scincidae, _38_

_Scincus_, _38_; scutes, 271

Sciuromorpha, _47_

Sclerotic, turtle, 228

Screamer, _41_; spurs, 330

Scutes, armadillos, 419; crocodile, 237; reptiles, 271

Scylliidae, _32_

_Scyllium_, _32_; calcification of vertebrae, 114; pectoral fins, 130; suspensorium, 119; see Dogfish

_Scymnus_, _32_, _118_; calcification of vertebrae, 114; mandibular arch, 120; pectoral fins, 130

_Scythrops_, _42_; interorbital septum, 333

Sea leopard, _48_; see _Ogmorhinus_; -- lion, _48_; manus, 511; pes, 526; position of limbs, 29; -- otter, _48_; pes, 526

Seal, _369_; manus, 511; pes, 526; sacral vertebrae, 452; scapula, 497

Secondaries, duck, 303 f.

Secretary-bird, _41_; claws, 330

Selachii, _31_; general characters, 63; teeth, 108

Selenodont, defined, 345, 428

Sella turcica, crocodile, 247; dog, 386

Semionotidae, _33_

Semiplumae, 328

Sense capsules, see Auditory, Nasal and Optic capsule

_Seps_, 38; limbs, 289

Shagreen, 61

Shaft of feather, 302

Shark, 64; Frill-gilled --, _31_; see _Chlamydoselache_; Port Jackson --, _32_; see _Cestracion_

Sheep, _359_; manus, 507; teeth, 345

Shields of turtle, 214

Shin, 26; see Crus

Shoulder girdle, see Pectoral girdle

Shrew, _49_, _370_; auditory ossicles, 488; cervical vertebrae, 446; presternum, 490; skull, 481; teeth, 440

Sigmoid notch, dog, 406

Siluridae, _33_; plates, 105

_Simia_, _49_; ribs, 493; skull, 484; thoraco-lumbar vertebrae, 450

Simiidae, _49_, _373_

Simplicidentata, _47_, 366

_Siphonops_, _35_; _S. annulatus_, skull, =178=

_Siredon_, _35_; skull, 175; teeth, 169; visceral arches, =181=

_Siren_, _35_, _135_, 188; beaks, 168; branchial arches, 180; digits, 187; skull, 174; teeth, 169

Sirenia, _44_, 522; arm bones, 501; caudal vertebrae, 453; cervical vertebrae, 443; general characters, 352; hair, 416; horny plates, 418; manus, 505; pectoral girdle, 495; pelvis, 514; ribs, 491; skull, 459; sternum, 489; teeth, 425; thoraco-lumbar vertebrae, 448

Sirenidae, _35_

Sirenoidei, _34_; general characters, 70

_Sivatherium_, _46_; skull, 469

Skate, _32_

Skeletogenous layer, 14, 16; _Amphioxus_, 52, 112

Skeleton, defined, 1; Cape Buffalo, =492=; _Ceratodus_, =128=; cod, 83 f.; crocodile, 237 f.; dog, 374 f.; duck, 302 f.; frog, 151 f.; llama, =496=; newt, 138 f.; turtle, 214 f.

Skink, _38_; see _Tiliqua_

Skull, 16 f.; Amphibia, 173 f.; Anura, 179 f.; birds, 333 f.; cod, 96 f.; crocodile, 243 f.; diagram of Mammalian, 385; Dipnoi, 124; dog, 383 f.; dogfish, 73 f.; donkey, =431=; duck, 312 f.; fish, 117; frog, 154 f., =159=; _Globicephalus_, =463=; Gymnophiona, 177; Indian elephant, =474=; Mammalia, 455; Marsipobranchii, 57; pig, =466=; _Procavia_, =433=; reptiles, 276 f.; Rhinoceros, =421=; _Rhytina_, =460=; sloth, =458=; Tasmanian wolf, =456=; Teleostei, 124; turtle, 222 f.; wombat, =456=

Sloth, _43_, _352_; auditory ossicles, 487; arm bones, 500; claws, 418; leg bones, 517; manus, 505; pectoral girdle, 495; pelvis, 513; pes, 522; ribs, 491; sacrum, 452; skull, 457; sternum, 489; teeth, 424; thoraco-lumbar vertebrae, 447

Snake, _38_; see Ophidia

Sole, _33_

_Solea_, _33_

_Solenodon_, _49_; teeth, 440

Solenodontidae, _49_

Solitaire, _42_, _330_; wing, 338; wrist, 330

_Sorex_, _49_; pelvis, 515; see Shrew

Soricidae, _49_; skull, 481

Spalacidae, _47_

_Spatularia_, _32_; distribution, 66

_Spelerpes_, _35_; branchial arches, 180; ribs, 182; _S. belli_ teeth, 169

Sperm whale, _44_, _357_; see _Physeter_

_Sphargis_, _37_; see _Dermochelys_

Sphenethmoid, frog, 156

Sphenisci, _40_; see Penguins

Sphenisciformes, _40_

_Sphenodon_, _37_, 197 f.; carpus, 291; cervical vertebrae, 275; fossae in skull, 281; humerus, 290; interparietal foramen, 277; ribs, 286; skull, =282=; tarsus, 293; teeth, 274

Sphenodontidae, _37_

Sphenoidal fissure, dog, 388

Sphenotic, 20; cod, 97; salmon, 89

Spider monkey, _49_; see _Ateles_

Spinacidae, _32_

Spinal column, 13; Dipnoi, 113; fish, 112; Holocephali, 113; Marsipobranchii, 56

Spines, Elasmobranchs, 61; mammals, 417

Spiny ant-eater, _43_; see _Echidna_; -- mouse, 47; see _Acanthomys_

Splenial, 22; crocodile, 258; duck, 320; turtle, 231

Spurs, birds, 330; Monotremata, 418

Spur-winged goose, 330; -- plover, 330

Squalidae _31_, _64_

_Squalodon_, _45_, _357_; dental formula, 427

Squalodontidae, _45_

Squamata, _37_; general characters, 198; position of teeth, 272; skull, 278

Squamosal, 21; crocodile, 256; dog, 394; duck, 316; frog, 160; newt, 144; turtle, 229

_Squatina_, _32_; calcification of vertebrae, 114; labial cartilages, 119; tail, 63; vertebral column, 114

Squatinidae, _32_

Squirrels, frontals, 476; pes, 526

Stapes, dog, 393; frog, 157; man, dog, rabbit, =485=; newt, 141

Steganopodes, _41_

Stegosauria, _39_; general characters, 209

Stegosauridae, _39_

_Stegosaurus_, _39_, _208_ f.; exoskeleton, 272

Steller's sea-cow, _44_; see _Rhytina_

Stereornithes, _41_

Stereospondyli, _35_

Sternal ribs, crocodile, 259; dog, 402; duck, 320; mammals, 490 f.

Sternebra, dog, 404

Sternum, 24; Amphibia, 182; birds, 336; crocodile, 260, =261=; dog, =403=; duck, 321; frog, 163; Mammalia, 489; newt, 145; reptiles, 287

Stork, 335; White --, _41_

Striges, _42_; see Owls

_Stringops_, _42_; sternum, 336

_Struthio_, _40_, _299_; see Ostrich

Struthiornithes, _40_, _299_

Sturgeon, _32_; see _Acipenser_

Stylo-hyal, dog, 399

Suborbital bar, duck, 318; -- ridge, dogfish, 76

Subplantigrade, defined, 358 n.

Subungulata, _46_; arm bones, 502; general characters, 360; manus, 509; pelvis, 514; pes, 525; shoulder girdle, 497; skull, 471; teeth, 432; thigh and shin, 519

Suidae, _45_

Suina, _45_, 358 f.; fibula, 519; manus, 507; odontoid process, 445; pelvis, 514; pes, 523; ulna, 501

Sula, _41_; see Gannet

Supinator ridge, dog, 406

Supine position, defined, 29

Supra-angular, 22; crocodile, 258; duck, 319; turtle, 230 f.

Supracaudal shield, turtle, 214

Supraclavicle, cod, 102

Supra-occipital, 19; crocodile, 247; dog, 386; duck, 315; turtle, 224

Supra-orbital, 20; crocodile, 251

Suprapharyngeal bone, cod, 101

Suprascapula, crocodile, 263; frog, 162

Supratemporal arcade, crocodile, 256; reptiles, 281

Surinam toad, _36_; see _Pipa_

Sus, _45_; dental formula, 428; see Pig

Suspensorium, Amphibia, 173; dogfish, 78; duck, 319; frog, 160; newt, 144; Pisces, 61

Sutures, 12

Swan, _41_; cervical and thoracic vertebrae, 332

Swift, _42_, 335; foot, 342

Symplectic, cod, 100; salmon, 94

Tails, fish, 60

Talpa, _49_; pelvis, 515; see Mole

Talpidae, _49_

Tapir, _46_, 360; malleus, 487; pes, =524=, 525; teeth, 345; see _Tapirus_

Tapiridae, _46_; dental formula, 429

_Tapirus_, _46_; fibula, 519; manus, =508=; skull, 471; see Tapir

Tarsier, _49_

Tarsiidae, _49_

_Tarsipes_, _43_, 349; mandible, 457

_Tarsius_, _49_, 372; pes, 527

Tarso-metatarsus, duck, 327

Tarsus, 26 f.; crocodile, 268; dog, 414; frog, 166; newt, 150; turtle, 236

Tasmanian devil, _43_; see _Sarcophilus_; -- wolf, _43_; see _Thylacinus_

_Tatusia_, _44_; stapes, 487; teeth, 424

Tectospondyli, 114

Tectrices, duck, 306

Teeth, =6=; Amphibia, 169; birds, 330; cod, 83; crocodile, 238; development, 7; dog, 374 f.; fish, 106 f.; frog, 158 f.; horses, 5; mammals, 344, 420 f.; pharyngeal, 8; reptiles, 272 f.; structure, 4; succession, 7

Teleosauridae, _39_

_Teleosaurus_, _39_; palate, 281; scutes, 271; vertebrae, 275

Teleostei, _33_; general characters, 69; ribs, 126; skull, 124; tail, 117; teeth, 110; vertebral column, 115

Temnospondyli, _35_

Tenrec, _49_; see _Centetes_

Tentorium, dog, 392

Terrapin, _37_

_Testudo_, _37_, _194_

_Tetraceros_, _46_; horns, 417

_Thalassochelys_, carapace, =216=

Thecodont, defined, 273

Theriodontia, _36_

Theromorpha, _36_; general characters, 191; humerus, 290; pectoral girdle, 288; ribs, 285; skull, 278; teeth, 273; vertebral column, 275 f.

Theropoda, _38_; general characters, 207; teeth, 273

Thoracic ribs, crocodile, 259; see Ribs; -- vertebrae, 16; crocodile, 241, =242=; dog, 381, =382=; duck, 310; turtle, 221

Thoraco-lumbar vertebrae, mammals, 447 f.

Thornback skate, 104

_Thylacinus_, _43_; atlas, 443; dental formula, 423; pelvis, 513; pes, 521; skull, =456=

_Thylacoleo_, _43_; skull, 457

Thyro-hyal, dog, 399

Tibia, 26; crocodile, 268; dog, 412; newt, 149; turtle, 235

Tibiale 27; see Tarsus

Tibio-fibula, frog, 166

Tibio-tarsus, duck, 326

Tichorhine Rhinoceros, 470

Tiger, _48_

_Tiliqua_, _38_; scutes, 200, 271

Tillodontia _47_, 365; femur, 520; manus, 511; teeth, 435

Tinamidae 300; caudal vertebrae, 333; vomers, 334

Tinamiformes, _41_

_Tinamus_, _41_; ischia, 341

Titanotheriidae, _46_; skull, 470; teeth, 432

_Titanotherium_, _46_; humerus, 501; manus, =508=; pes, 525

Toad, _36_; shoulder girdle, 185

Tope, _32_

Torpedinidae, _32_

_Torpedo_, _32_, 104

Tortoise, _37_; position of limbs, 28

_Tortrix_, ischio-pubis, 292; traces of posterior limb, 293

Toucan, _42_; foot, 342

_Toxodon_, _46_, 361; femur, 519; pes, 525; teeth, 432

Toxodontia, _46_; general characters, 361; manus, 509; skull, 472; teeth, 432

Toxodontidae, _46_

Trabeculae 11; -- cranii, 17

Tragulidae, _45_

Tragulina, _45_, 359; fibula, 519; manus, 507; odontoid process, 445; pes, 523; skull, 468; teeth, 429; ulna, 501

Transpalatine, crocodile, 255; reptiles, 278

Trapezium, 27; dog, 408

Trapezoid, 27; dog, 408

Trichechidae, _48_, 369

_Trichechus_, _48_; see Walrus

Trionychia, _37_; general characters, 194

Trionychidae, _37_

_Trionyx_, _37_, 193 f.; exoskeleton, 214, 270; skull, 283; vestiges of teeth, 274

_Trissolepis_, _32_; scales, 104

_Tritylodon_, _43_; teeth, 348

Trochanter, dog 412; duck, 326

Trochilidae, _42_; see Humming-birds

Trochlea, crocodile, 263; dog, 405 f.; duck, 323; turtle, 232

Trogon, _42_; foot, 342

Trogonidae, _42_

_Tropidonotus_, _38_; jaws, 280; skull, =279=

Trunk vertebrae, cod, 84; see thoracic and lumbar vertebrae

_Trygon_, _32_; calcification of vertebrae, 114; caudal spine, 106

Trygonidae, _32_

Tuberosities of humerus, dog, 405; of ischium, dog, 411

Tunicata, _30_, 51

_Tupaia_, skull, 480; thoraco-lumbar vertebrae, 450

Turbinals, dog, 395

_Tursiops_, _45_; skull, 462

Turtle, _37_; anterior limb, 232, =234=; cranium, 222 f., =226=; hyoid, 231, =285=; mandible, 230; pectoral girdle, 231; pelvic girdle, 235; pes, 236; plastron, 217, =218=; posterior limb, =234=, 235; sense capsules, 227; skull, 222; vertebral column, 219; Leathery --, see _Dermochelys_; Snapping --, see _Trionyx_

Tylopoda, _45_, 359; fibula, 519; manus, 507; odontoid process, 445; pelvis, 514; pes, 523; skull, 468; teeth, 428; ulna, 502

Tympanic, dog, 392; -- cavity, crocodile, 250; diagram of mammalian, =391=; dog, 393; duck, 315 f.; turtle, 228; -- recess, duck, 315

Tympano-hyal, dog, 399

Typhlopidae, _38_; scales, 270; skull, 278

_Typhlops_, _38_; ischio-pubis, 292; traces of posterior limb, 293

Typotheriidae, _46_

_Typotherium_, _46_, 358, 361; clavicle, 495, 497; femur, 519; pes, 525; skull, 472; teeth, 432

_Udenodon_, _36_, _192_; beak, 271

Uintatheriidae, _47_; skull, 364

_Uintatherium_, _47_; dental formula, 433; leg, 519; limbs and limb girdles, =516=; manus, 510; pelvis, 514; skull, 473

Ulna, 26; crocodile, 265; dog, 406; duck, 323; frog, 164; newt, 147; turtle, 233

Ulnare, 27; see Carpus

Umbilicus, inferior and superior, duck, 303

Uncinate process, 190; crocodile, 259; duck, 320

Unciform, 27, 345, 504; dog, 408

Ungulata, _45_; auditory ossicles, 487; caudal vertebrae, 453; cervical vertebrae, 445; general characters, 357; manus, 506; pectoral girdle, 495; pes, 522; ribs, 491; sacrum, 452; skull, 464 f.; sternum, 489; teeth, 427 f.; thoraco-lumbar vertebrae, 448

Ungulata vera, _45_; arm bones, 501; general characters, 358; manus, 506; pelvis, 514; thigh and shin, 519

Upper arm, 26; crocodile, 263; dog, 405; duck, 323; frog, 164; newt, 147; turtle, 232

_Upupa_, _42_; see Hoopoe

Urochordata, _30_, 51

Urodela, _35_; general characters, 134; pelvis, 187; ribs, 182; skull, 174

Urohyal, cod, 101; duck, 320

Urostyle, Anura 172; cod, 85; frog, 153; Teleostei, 117

Ursidae, _48_; humerus, 502

_Ursus_, _48_; dental formula, 439; see Bears

Vacuities, anterior palatine --, crocodile, 252, 258; -- in reptilian skull, 281; posterior palatine --, crocodile, 254, 257; pre-orbital --, reptiles, 283 f.

Vampire, _49_; teeth, 441

Vane, of feather, 303

Varanidae, _38_

_Varanus_, _38_; shoulder girdle, =202=; skull, =201=

Vasodentine, 108, 272

Vertebral column, 14; Amphibia, 170; birds, 332; cod, 83; crocodile, 239; dog, 378; duck, 307; Elasmobranchs, 113; frog, 152; mammals, 442; newt, 138; turtle, 219; -- ribs, crocodile, 259; dog, 402; duck, 320; -- shield, turtle, 214

Vertebrata, general characters, 53

Vexillum, of feather, 303

Vibrissae, dog, 374

Viscacha, _47_

Visceral skeleton, 21; dogfish, 77; Elasmobranchs, 119 f.

_Viverra_, _48_; acetabular bone, 515

Viverridae, _48_

Vomer, 21; cod, 98; crocodile, 252; dog, 395; duck, 317; frog, 158; salmon, 93; turtle, 229

Vomero-palatine, newt, 143

_Vultur_, _41_

Vulture, _41_; Black --, shoulder girdle and sternum, =337=

Waders, 335

Walrus, _48_, 367, 369; canines, 420; manus, 511; pes, 526; position of limbs, 29; skull, 480; teeth, 440

Warblers, _42_

Wart hog, _45_; teeth, 428

Weasel, _369_

Whale, baleen, 3, 418; Ca'ing --, _45_, see _Globicephalus_; Humpbacked --, _44_, 357; Right --, _44_, 357; Sperm --, _44_, 357, see _Physeter_; True or Whalebone --, 356

Whiting, _33_

Wild duck, _41_; see Duck

Wing, duck, 322; Gannet, Ostrich, and Penguin, =339=

Wolf, _48_

Wombat, _43_; atlas, 443; pes, 521; sacrum, 451; skull, =456=; tail, 453; teeth, 423

Woodpecker, _42_, 335; foot, 342; hyoid, 336

Wrasse, _33_; teeth, 111

_Xenacanthus_, _31_; pectoral fins, 130

Xenopidae, _36_

_Xenopus_, _36_; branchial arches, 182; nails, 168; pelvis, 188; ribs, 182

Xiphiplastron, turtle, 217

Xiphisternal horn, crocodile, 260

Xiphisternum, dog, 404; frog, 163

Xiphoid process, duck, 321

_Zeuglodon_, _44_, 353, 356; dental formula, 426; dermal plates, 420

Zeuglodontidae, _44_

Zygantra, defined, 199 n.; reptiles, 276

Zygapophyses, cod, 84; crocodile, 240 f.; dog, 379 f.; duck, 308 f.; frog, 152 f.; newt, 139; turtle, 219 f.

Zygosphene, defined, 199 n.; reptiles, 276

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Transcriber Notes

Italic text is denoted by _underscores_ and bold text by =equal signs=. Subscripts are represented using braces, e.g. V{1}, and superscripts are introduced with a caret, e.g. 2^e

Obvious punctuation and spelling errors, and inconsistent hyphenation have been corrected.

The oe ligature in the text has been replaced with the characters oe.

End of Project Gutenberg's The Vertebrate Skeleton, by Sidney H. Reynolds