Part 10

This genus is represented by five species. MICROCHÆRUS ANTIQUUS (Filhol) is of very small size, and has many affinities with _Galago_, as exhibited in the well-preserved cranium that has been recovered from the Phosphorites of Central France. The two lower molars have only one root. M. ERINACEUS, {116}Wood, from the Upper Eocene of Hampshire; M. EDWARDSI (Filhol), from Central France, a species larger than _M. antiquus_, presents dental characters similar to the Galagos and the Mouse-Lemurs; M. PARVULUS (Filhol), and M. ZITTELI (Schlosser), are both from the Quercy Phosphorites of France; while M. ARMATUS is from the Eocene of Alsace, and M. (CRYPTOPITHECUS) SIDEROLITHICUS from the Bonerg of Frohnstellen.

GENUS MIXODECTES.

_Mixodectes_, Cope, Proc. Amer. Phil. Soc., p. 447 (1883); id., Rep. U. S. Geol. Surv., iii., p. 240, pl. xxiv. f, figs. 1 and 2.

The members of this genus, founded on fragmentary mandibles from the Puerco (Lower Eocene) strata of New Mexico, have a large front tooth "issuing from the ramus at the symphysis like a rodent incisor, the second tooth being similar but smaller and posterior and external to the first." The genus is represented by two species, M. PUNGENS, Cope, and M. CRASSIUSCULUS, Cope.

GENUS CYNODONTOMYS.

_Cynodontomys_, Cope, Palæont. Bull., p. 151 (1882); id., Rep. U. S. Geol. Surv., iii., p. 243, pl. xxiv., fig. 2.

This genus contains but one species, founded on several lower jaws disinterred from the Wasatch beds in the Big-Horn Bad-lands, in Northern Wyoming. The lower incisors, or perhaps, canines, are very large and close to the line of union of the two halves of the jaw; the molars have three cusps in front and a heel behind. The dental characters of the genus "resemble considerably those of _Anaptomorphus_ and _Necrolemur_ [_Microchærus_] but the large size of the inferior canine {117}or incisor tooth distinguishes it from both." (Cope.) C. LATIDENS, Cope, is the only species.

GENUS OMOMYS.

_Omomys_, Leidy, Journ. Acad. Nat. Sci. Philad., vii., p. 408 (1869).

This genus was established for the first Mammalian fossil--a lower jaw--described from the Bridger-beds as O. CARTERI. The posterior lower molar has cusps in opposing pairs; pre-molars, three in number, the two anterior one-cusped, the posterior two-cusped. The chin was longer and less rounded than in _Anaptomorphus_.

GENUS ANAPTOMORPHUS.

_Anaptomorphus_, Cope, Proc. Amer. Phil. Soc., 1872, p. 554; id., Rep. U. S. Geol. Surv., iii., p. 245, pl. xxiv. e, fig. 1; xxv., fig. 10.

This genus was founded by Cope on an almost entire cranium discovered in the Bridger (Eocene) beds of the upper Valley of Green river, and on other remains from what is known as the Wasatch formation of the Big-Horn Basin in Wyoming Territory, in North America. The external upper incisor is small and set close to the small canine; the pre-molars have each a large external and a smaller internal cusp; the true molars are wide and have one internal and two external cusps. In the lower jaw the two anterior molars are four-cusped, with a transverse ridge between the anterior pair, and an oblique ridge between the hind inner, and the front outer, cusp; the posterior is three-cusped and has a heel. The orbits are enclosed, as in typical Lemurs. Not less typical characters are the position of the lachrymal foramen, external to the orbit, and the unossified halves of the lower jaw. "Its dental formula (I2/2, {118}C1/1, P2/2, M3/3) agrees only with the _Indrisinæ_. But no known _Lemuridæ_ possess anterior lobes and cusps on all the pre-molars, so that in this respect, as in the number of its teeth, this genus resembles the higher Monkeys, the _Simiidæ_ and _Hominidæ_, more than any existing member of the family.... It has ... a number of resemblances to _Tarsius_, which is, perhaps, its nearest ally among the Lemurs, although that genus has three pre-molars.... There is no doubt but that the genus _Anaptomorphus_ is the most Simian Lemur yet discovered...." (_Cope._)

The species included in this genus are A. ÆMULUS (Cope), which did not exceed the size of a Marmoset or a Red Squirrel, and had short erect incisors; A. HOMUNCULUS (Cope), a species founded on a cranium without a lower jaw, with the orbits not so large as in _Tarsius_, and the skull wide behind the eyes. "The _A. homunculus_ was nocturnal in its habits," according to Professor Cope, "and its food was like that of the smaller Lemurs of Madagascar and the Malayan islands. Its size is a little less than that of the _Tarsius tarsius_."

Two other insufficiently characterised genera, both considered to be primitive Lemuroids, are _Plesiadapis_, Gervais, containing the species P. REMENSIS, P. GERVAISI, P. TOURNESARTI, and P. DAUBREI, from the Lower Eocene strata of Rheims, which have five-cusped lower molars, and enlarged upper and lower incisors; and _Protoadapis_, Lemoine, with one or two high front cusps, and a low heel to its three pre-molars; the anterior molars with two pairs of opposite cusps, the posterior molar with a fifth cusp on the hind border. P. CRASSICUSPIDENS, Lemoine, and P. RECTICUSPIDENS, Lemoine, are its two species.

{119}FAMILY ADAPIDÆ.

The different species associated together under this family are abundantly known from the Upper Eocene of France, England, and North America. They are remarkable in having an extra pre-molar in both jaws, the dental formula being I2/2, C1/1, P4/4, M3/3.

GENUS ADAPIS.

_Adapis_, Cuvier, Ossem. Foss. (2) iii., p. 265 (1822); Flower, Ann. and Mag. N. H., xvii., (1876), p. 323.

_Palæolemur_, Delfort., Act. de la Soc. Linn. Bord., xxix., pp. 87-95, pl. 5 (1873); id. C. R., lxxvii., p. 64 (1873).

_Aphelotherium_, Gervais, Zool. et Pal. Franç. (1), ii., Exp. 34 (1848-52).

_Cænopithecus_, Rütim, Denksch. Schw. Ges. Nat., xix., p. 88 (1862).

_Notharctus_, Leidy, Geol. Surv. Mont., p. 364 (1871).

_? Thinolestes_, Marsh, Am. Jour. Sci., 1872 (2), p. 205.

_? Telmalestes_, Marsh, _op. cit._, p. 206.

"The general form of the cranium," to quote Sir W. Flower, "the large size and anterior direction of the orbits, the small and narrow muzzle ... show its affinity to the Lemurine animals, and especially to the African forms. The whole skull, however, is more depressed than in the slow Lemurs and Galagos; the orbits are smaller, the brain cavity relatively smaller and more constricted behind the orbits, and the muscular ridges more developed."... The lower jaw is deep and stout. The posterior upper pre-molar is very similar to a true molar. "The upper molar teeth are nearly equal in size, and have nearly square crowns, with four distinct cusps, one at each angle, rather obliquely placed"; the hind inner cusp {120}of the posterior molar inconspicuous. The lower molars have two pairs of obliquely placed cusps, connected by transverse ridges, anterior and posterior, with an oblique ridge running forwards and inwards from the outer hind cusp. The hindmost lower pre-molar has an internal cusp; the lower incisors have upright spatulate crowns like those of true Apes.

Several species of this genus have been described. ADAPIS PARISIENSIS (with the synonyms of _Aphelotherium duvernoyi_, Gervais, and _Palæolemur betillei_, Delfortrie) is one of the best known, and its remains have been found in Upper Eocene strata at Egerkingen, in Switzerland, at Sainte Néboule de Béduer, and in the Paris Gypsum, in France, as well as in England. It "more nearly resembles the Indo-African Lemurs, and not those of the island of Madagascar, or of the extreme east, having no near relationship with the Tarsius, the Aye-Aye, or the Indris, and not much with the true Lemurs." (_Flower._) From the Eocene of Switzerland comes A. LEMUROIDES. ADAPIS MAGNA (Filhol) is larger than the preceding species, has a larger face, and a greater constriction between the cerebral and facial regions of the skull. It has been found in the phosphatic deposits at Raynal, in France. ADAPIS ANGUSTIDENS (Filhol), from the Quercy Phosphates of France, is distinguished by the structure of its molars, and by the great size of its two anterior pre-molars. A. TENEBROSUS (Leidy) has a large lower canine. A. MINOR (Filhol) is an additional species.

GENUS TOMITHERIUM.

_Tomitherium_, Cope, Vert. Bridg. Eoc. Wyom., p. 2, 1872.

_Limnotherium_, Marsh, Am. Journ. Sci., 1871, ii., p. 43 (in part).

This genus, which is allied to _Adapis_, is characterised by {121}having its lower incisors with cutting edges; the first and second lower pre-molars with one root; the third with one cusp and a posterior heel, and the fourth an interior lateral cusp in addition. The lower true molars have two anterior cusps (the inner being double) and two posterior. The thigh is long and the knee free from the body as in the _Anthropoidea_, the hand capable of turning freely upwards at the wrist; the hind-limbs longer than the fore-, and "the details of the lower jaw, which is co-ossified in the centre, and teeth similar to that of the lower Monkeys." The remains of the only known species, T. ROSTRATUM (Cope), which was about the size of the Capuchin Monkey (_Cebus capucinus_) of Brazil, were found in the Bridger (Eocene) beds in an isolated spot on Blacks' fork, Wyoming.

GENUS MENOTHERIUM.

_Menotherium_, Cope, Bull. U. S. Geol. Surv. Territ., 1874, i., p. 22.

_Laopithecus_, Marsh, Am. Journ. Sei., 1875, i., p. 240.

This genus was established on an under jaw from the Lower Miocene White-river beds of Nebraska. Its molars are successively larger from anterior to posterior; the two pairs of cusps are obliquely opposite, the hinder pair longer than the front pair, and presenting a strong cingulum. Its discovery was the first indication of Lemurs in the Miocene of the United States. M. ROBUSTUM, Marsh, was as large as a Coati; and M. LEMURINUM (Cope) about the size of a domestic Cat.

GENUS PELYCODUS.

_Pelycodus_, Cope, Cat. Verteb. Eoc. New Mex., p. 13 (1875).

_Tomitherium_, Cope, Rep. U. S. Geol. Surv. W. of 100° mer., ii., p. 135 (in part).

_Lemuravus_, Marsh, Amer. Journ. Sci., 1875, i., p. 239.

{122}This genus is characterised by the second pre-molar having always two roots; the anterior has one root and the third three; the posterior has one external and one internal cusp. Of the true molars, all have two external cusps; the anterior and median have two internal cusps and the posterior has only one; of the lower teeth the posterior pre-molar has an internal cusp and a heel; the next one has no internal cusp; the molars often have the fore inner cusps double; the posterior molar has a strong heel. This genus contains three species, all described by Cope (P. JARROVII, P. TUTUS, P. FRUGIVORUS), with the hind inner cusp of the upper molars distinct from the heel; and P. ANGULATUS, in which that cusp is small and is on the heel. Their remains have been found in the Lower Eocene (Wasatch) beds of New Mexico. P. HELVETICUS has been described from the Upper Eocene of Egerkingen.

GENUS MICROSYOPS.

_Microsyops_, Leidy, Proc. Acad. Nat. Sci., Philad., 1872, p. 20.

_Limnotherium_, Marsh, Amer. Journ. Sci., 1871, ii., p. 43 (in part).

This genus is easily distinguished, as Cope points out in his sumptuously illustrated "Vertebrata of the Tertiary Formations of the West," by the absence of the first (anterior) inferior pre-molar, and probably of the superior first pre-molar also. The canine tooth of the lower jaw is very large. The posterior pre-molar has an internal cusp, and the molars two front inner cusps. There are three species, distinguished chiefly by size, M. SPIERIANUS (Cope), very small; M. ELEGANS (Marsh), the largest, with seven teeth succeeding the canine in the lower jaw; and M. SCOTTIANUS (Cope); all from the Eocene of Wyoming.

{123}GENUS HYOPSODUS.

_Hyopsodus_, Leidy, Proc. Acad. Nat. Sci., Philad., 1870, p. 109.

The present genus is recognised by the front inner cusp of the lower molars being single, and their heel presenting a cusp at its inner hind angle (except in _H. acolytus_). Of the upper pre-molars, the median and posterior have an internal cusp; and the molars have two outer and two inner cusps with two small intermediate tubercles. There are six species known, from the Wasatch and Bridger beds of Wyoming and New Mexico, of which H. ACOLYTUS is distinguished by having the heel of the anterior and median lower molars without an inner hind cusp. Professor Cope remarks that though the species of this genus are not numerous, individuals of some of them are exceedingly common in the Eocene beds of Wyoming. H. PAULUS and H. MINUSCULUS, Leidy, H. VICARIUS and H. POWELLIANUS, Cope, with H. JURENSIS, Rutimeyer, from the Upper Eocene of Egerkingen, are the best known species.

The genera INDRODON, Cope, from the Lower Eocene Puerco formation of New Mexico, with three cusped upper and four cusped lower molars; OPISTHOTOMUS, APHELISCUS, and SARCOLEMUR, Cope, from the Wasatch of Wyoming; HIPPOSYUS, Leidy; BATHRODON, MESACODON, and STENACODON, Marsh, from the Middle Eocene Bridger beds; are of doubtful affinities.

II. THE MONKEYS AND APES--SUB-ORDER ANTHROPOIDEA.

This Sub-order, though containing animals of much higher organisation than the _Lemuroidea_, embraces species presenting many different grades of intelligence, and ranging in size from the Pigmy Marmoset, not larger than a small Kitten, to the {124}ponderous Gorilla and the genus _Homo_. In external characters the Monkeys and Apes have in general a shorter and less Dog-like nose than the Lemurs, thin lips and a more distinct face; while their eyes, situated on the face, are invariably directed forwards, and never outwards, or to the side. The opening of their nostrils is either outward (as in those inhabiting the New World), or downwards (as in the bulk of the Old World species). All of them are covered with hair; the tail may be long, short, or wanting. The proportions of the fore-limbs to the hind- vary much in the different groups. The great toe, as well as the thumb, is (except in a few species) fully opposable, so that in the majority of members of the Sub-order, the foot is as good a prehensile organ as the hand. From this circumstance comes the designation, _Quadrumana_, or "four-handed," so often applied to these animals. In a few species the thumb is rudimentary or absent, but the fore-finger, the absence of which characterised some of the Lemurs, is always present and well developed, and the corresponding digit in the foot (except in the Marmosets) has a flat nail instead of a claw. The mammæ of the _Anthropoidea_ are always situated on the breast. If we examine the structures underlying the skin, we find that in the skull the orbits are entirely shut in by a bony wall, so that the finger cannot be passed into the temporal depression behind, as could be done in the Lemurine skull, and that the lachrymal foramen opens within the cavity for the eye. In the present Sub-order there is no toothless space in the mid-line of the upper jaw, the incisor teeth being set close together; but there is always a vacuity, except in Man, between the incisors and the canine tooth. The lower canine teeth do not resemble in form the incisors, nor do they protrude horizontally, as in the Lemurs. {125}The two halves of the lower jaw are always co-ossified together, when the animal is full grown. The _humerus_, or arm-bone, never has an entepicondylar foramen on the inner side of its lower portion, and the bones of the fore-arm (the _ulna_ and _radius_) are never ossified together, nor are those of the lower leg (the _tibia_ and _fibula_); so that there is perfect freedom for every movement necessary for grasping and walking, or for rotating the hand or foot on the wrist and ankle.

With regard to the brain, the anthropoid cerebrum, or fore-brain, is greatly convoluted, and differs from that of the Lemurs by its proportionately larger size, the cerebellum, or hind-brain, being as a rule entirely covered by it.

The uterus and structures for the nutrition of the young prior to birth differ greatly in this Sub-order from the conditions existing in the _Lemuroidea_. The uterus is a simple and not a two-horned sac, and its inner layer, in which the foetal and maternal structures intermingle during the growth of the embryo, is shed after the birth of the young, which is not the case in the Lemurs.

"The resemblance of Monkeys to Man," says Mr. Darwin, "is greatly caused by the relative position of the features of the face. The eyes are arched over; they are separated by a long nose, the end of which in some is very human. The mouth is not carried back, but occupies the same general position as in Man, and the forehead, so often wrinkled, is usually prominent and like that of a child. The likeness is increased by the fact that anger, sorrow, pleasure, and satisfaction, are displayed by the Monkey by nearly similar movements of the muscles and skin, chiefly above the eyebrows and round the mouth. Some few expressions are indeed almost the same, as in the weeping of certain kinds of Monkeys, and in the {126}laughing noise made by others, during which the corners of the mouth are drawn backward and the eyelids wrinkled. In Man the nose is much more prominent than in most Monkeys; but we may trace the commencement of an aquiline curvature in the nose of the Hoolock Gibbon, and this in the Great-nosed Monkey (_Nasalis larvatus_) is carried to a ridiculous extreme."

In regard to the distribution of the _Anthropoidea_, excluding Man (_Hominidæ_), two families (the _Hapalidæ_ and _Cebidæ_) are known only from the New World; and two others (the _Cercopithecidæ_ and _Simiidæ_) are exclusively confined to the Old World. No fossil remains of Eastern Hemisphere forms have as yet been found in the Western, or _vice versâ_, a fact which indicates, doubtless, a separation of great antiquity between the two groups. The various species of these families are to be found chiefly in the warmer regions on both sides of the equator. In the New World some species range as far north as to 20° N. lat. in Mexico; and South, to 30° below the equator. In the Eastern Hemisphere, the Old World species predominate in the tropical and sub-tropical regions; but certain forms have spread as far north as Thibet and Japan, and others have made the high altitudes of the Himalaya Mountains their home; while to the southward they extend in Africa nearly to the Cape of Good Hope. No indigenous species have ever been found in New Guinea, Australia, New Zealand, or in the Pacific, or West Indian Islands.

The Apes of the Old World differ in many important characters from those of the New. Among the former, as already mentioned, the openings of the nostrils are directed downwards, as in Man; the nose is narrow, and the nostrils themselves are set close together, being separated from each other by a thin septum, or partition, of cartilage. On this account, {127}they have received the name of Catarrhine Monkeys (_Catarrhini_).[7] The New World Monkeys, on the other hand, have the nose flat and the opening of their nostrils directed outwards, and the one nostril widely separated from the other by a broad cartilaginous septum, and they are therefore designated Platyrrhine Monkeys (_Platyrrhini_).[8]

The dental formula of the Old World forms is I2/2, C1/1, P2/2, M3/3, making a total of thirty-two teeth in all; but those of the Western Hemisphere differ in having invariably three pre-molars, and sometimes two molars, instead of three, so that they possess either thirty-two or thirty-six teeth altogether. There is always a gap, or _diastema_, in the series of the teeth in front of the upper and behind the lower canines; the latter teeth being taller than the rest. Many of the Catarrhine Apes have large cheek-pouches as well as bare patches, or callosities, often brightly coloured, on the part they apply to the ground when sitting. None of the Platyrrhine group have cheek-pouches or callosities, but in many of them the tail is marvellously prehensile, which is not the case in any of the Old World species. Again, in the Apes of the Eastern Hemisphere, the ear-capsules of the skull have an external bony channel (or _meatus_) for conveying the sound vibrations into the ear, which is absent in the American species.

As a rule the Platyrrhine Monkeys have the fore-limbs shorter than the hind-, and are more quadrupedal than those of the Old World. Their thumb is also more like a finger than the same digit in their Eastern brethren.

Of the New World Monkeys, the _Hapalidæ_, or Marmosets, have thirty-two teeth, and the _Cebidæ_, with several {128}sub-families, have thirty-six teeth. The former include the Marmosets (_Hapale_) and the Tamarins (_Midas_). The latter comprise the Capuchins (_Cebus_), which may be taken as the representative genus of American Monkeys, the Woolly Monkeys (_Lagothrix_), the Spider-Monkeys (_Ateles_ and the allied _Eriodes_), the Howlers (_Mycetes_), the Sakis (_Pithecia_ and _Brachyurus_), the Night-Monkeys or Douroucolis (_Nyctipithecus_), and the Squirrel Monkeys or Saimiris (_Chrysothrix_), with the allied _Callithrix_.

"The extensive equatorial forests of the Amazon and Orinoco, and their tributaries, constitute _par excellence_ the home of the American Monkeys, but the majority of the genera have a very extended range, appearing in one or more species throughout the greater portion of the tract covered by the entire family. This is more particularly the case with the Sapajous (_Cebus_), Spider-Monkeys, Howlers, and the species of _Callithrix_. The range of the species, on the other hand, is not unfrequently very sharply defined, as, for example, when a natural barrier, offering insurmountable obstacles to further migration, suddenly interposes itself. Examples of such limitation, as brought about by the dominant water-courses of the equatorial forests," are numerous. Mr. Wallace cites the case of certain species of Saki Monkey (_Pithecia_), found on either side of the Amazon river, whose range, either southward or northward, appears to be limited by that river. "The number of species of these American Apes found in, and north of, the Isthmus of Panama is ten, of which only one (_Ateles vellerosus_) extends into Mexico; _Mycetes villosus_, the Guatemalan Howler, or 'Mono,' has thus far been found only in Guatemala and Honduras. It is a little surprising that the range of only two of the species--the Black-faced Spider-Monkey (_Ateles ater_) {129}and one of the Night-Apes (_Nyctipithecus vociferans_)--extends beyond Colombia, in South America."

"None of the South American Monkeys appear to pass west of the Andean chain of mountains south of Ecuador, and even north of the Peruvian boundary the number of such transgressional forms is very limited. Indeed, even among the wooded slopes, a habitation along the basal line of the mountain axis seems to be much preferred. The greatest altitude at which Monkeys were observed by Tschudi in Peru was 3,000 feet (_Lagothrix humboldti_); _Ateles ater_ and _Cebus robustus_ were found at 2,500 feet. On the other hand, Salvin and Godman state that in the district of Vera Paz, in Guatemala, the 'Mono' or Howler is most abundant at an elevation of 6,000 feet; and on the Volcano of Atitlan, in the same country, Mr. Salvin found troops of the Mexican Spider-Monkey (_Ateles vellerosus_) in the forest region of 7,000 feet elevation.

"The range of the Marmosets and Oustitis (_Hapalidæ_) is nearly co-extensive with that of the Monkeys proper." (_Heilbrin._) The Pigmy and the Silky Marmoset range as far north as Mexico.

THE MARMOSETS AND TAMARINS. FAMILY HAPALIDÆ.