CHAPTER XXIX

THE BLENNIES: BLENNIIDÆ

THE great family of blennies, _Blenniidæ_, contains a vast number of species with elongate body, numerous dorsal spines, without suborbital stay or sucking-disk, and the ventrals jugular, where present, and of one spine and less than five soft rays. Most of them are of small size, living about rocks on the sea-shores of all regions. In general they are active fishes, of handsome but dark coloration, and in the different parts of the group is found great variety of structure. The tropical forms differ from those of arctic regions in the much shorter bodies and fewer vertebræ. These forms are most like ordinary fishes in appearance and structure and are doubtless the most primitive. Of the five hundred known species of blennies, we can note only a few of the most prominent. To _Clinus_ and related genera belong many species of the warm seas, scaly and ovoviviparous, at least for the most part. The largest of these is the great kelpfish of the coast of California, _Heterostichus rostratus_, a food-fish of importance, reaching the length of two feet. Others of this type scarcely exceed two inches. _Neoclinus satiricus_, also of California, is remarkable for the great length of the upper jaw, which is formed as in _Opisthognathus_. Its membranes are brightly colored, being edged with bright yellow. _Gibbonsia elegans_ is the pretty "señorita" of the coralline-lined rock-pools of California. _Lepisoma nuchipinne_, with a fringe of filaments at the nape, is very abundant in rock-pools of the West Indies. The species of _Auchenopterus_ abound in the rock-pools of tropical America. These are very small neatly colored fishes with but one soft ray in the long dorsal fin. Species of _Tripterygion_, _Myxodes_, _Cristiceps_, and other genera abound in the South Pacific.

In _Blennius_ and its relatives the body is scaleless and the slender teeth are arranged like the teeth of a comb. In most species long, fang-like posterior canines are developed in the jaws. _Blennius_ is represented in Europe by many species, _Blennius galerita_, _ocellaris_, and _basiliscus_ being among the most common. Certain species inhabit Italian lakes, having assumed a fresh-water habit. The numerous American species mostly belong to other related genera, _Chasmodes bosquianus_ being most common. _Blennius yatabei_ abounds in Japan. In _Petroscirtes_ and its allies the gill-openings are much restricted. The species are mainly Asiatic and Polynesian and are very prettily colored. _Petroscirtes elegans_ and _P. trossulus_ adorn the Japanese rock-pools and others, often deep blue in color, abound in the coral reefs of Polynesia.

The rock-skippers (Salarias, Alticus, etc.) are herbivorous, with serrated teeth set loosely in the jaws. These live in the rock-pools of the tropics and leap from rock to rock when disturbed with the agility of lizards. They are dusky or gray in color with handsome markings. One of them, _Erpichthys_ or _Alticus saliens_ in Samoa, lives about lava rocks between tide-marks, and at low tide remains on the rocks, over which it runs with the greatest ease and with much speed, its movements being precisely like those of _Periophthalmus_. As in the species of the latter genus, otherwise wholly different, this _Alticus_ has short ventral fins padded with muscle.

_Erpichthys atlanticus_ is found in abundance on both coasts of tropical America. Many species abound in Polynesia and in both Indies. _Salarias enosimæ_ lives in the clefts of lava rocks on the shores of Japan. _Ophioblennius_ (_webbi_) is remarkable for its strong teeth, _Emblemaria_ (_nivipes_, _Atlantica_) for its very high dorsal. Many other genera allied to _Blennius_, _Clinus_, and _Salarias_ abound in the warm seas.

=The Northern Blennies: Xiphidiinæ, Stichæiniæ, etc.=—The blennies of the north temperate and arctic zones have the dorsal fin more elongate, the dorsal fin usually but not always composed entirely of spines. The scales are small and the ventral fins generally reduced in size. These are divided by Dr. Gill into several distinct families, but the groups recognized by him are subject to intergradations.

_Chirolophis_ (_ascanii_) of north Europe is remarkable for the tufted filaments on the head. These are still more developed in _Bryostemma_ of the North Pacific, _Bryostemma polyactocephalum_ and several other species being common from Puget Sound to Japan. _Apodichthys_ (_flavidus_) of California is remarkable for a large quill-shaped anal spine and for the great variation in color, the hue being yellow, grass-green, or crimson, according to the color of the algæ about it. There is no evidence, however, that the individual fish can change its color, and these color forms seem to be distinct races within the species. _Xererpes fucorum_ of California lies quiescent in the seaweed (_Fucus_) after the tide recedes, its form, color, and substance seeming to correspond exactly with those of the stems of algæ. _Pholis gunnellus_ is the common gunnel (gunwale), or butter-fish, of both shores of the North Atlantic, with numerous allies in the North Pacific. Of these, _Enedrias nebulosus_, the ginpo, or silver-tail, is especially common in Japan. _Xiphidion_ and _Xiphistes_ of the California coast, and _Dictyosoma_ of Japan, among others, are remarkable for the great number of lateral lines, these extending crosswise as well as lengthwise. _Cebedichthys violaceus_, a large blenny of California, has the posterior half of the dorsal made of soft rays. _Opisthocentrus_ of Siberia and north Japan has the dorsal spines flexible, only the posterior ones being short and stiff. The snake-blennies (_Lumpenus_), numerous in the far North, are extremely slender, with well-developed pectorals and ventrals. _Lumpenus lampetræformis_ is found on both shores of the Atlantic. In _Stichæus_ a lateral line is present. There is none in _Lumpenus_, and in _Ernogrammus_ and _Ozorthe_ there are three. All these are elongate fishes, of some value as food and especially characteristic of the Northern seas. Fossil blennies are almost unknown. _Pterygocephalus paradoxus_ of the Eocene resembles the living _Cristiceps_, a genus which differs from _Clinus_ in having the first few dorsal spines detached, inserted on the head. The first spine alone in _Pterygocephalus_ is detached and is very strong. A species called _Clinus gracilis_ is described from the Miocene near Vienna, _Blennius fossilis_ from the Miocene of Croatia, and an uncertain _Oncolepis isseli_ from Monte Bolca. The family is certainly one of the most recent in geologic times. The family of _Blenniidæ_, as here recognized, includes a very great variety of forms and should perhaps be subdivided into several families, as Dr. Gill has suggested. At present there is, however, no satisfactory basis of division known.

=The Quillfishes: Ptilichthyidæ.=—The _Ptilichthyidæ_, or quillfishes, are small and slender blennies of the North Pacific, with very numerous fin-rays. _Ptilichthys goodei_ has 90 dorsal spines and 145 soft rays. Another group of very slender naked blennies is the small family of _Xiphasiidæ_ from the South Pacific. The jaws have excessively long canines; there are no ventral fins. The dorsal fin is very high and the caudal ends in a long thread.

=The Blochiidæ.=—Of doubtful relationship is the extinct family of _Blochiidæ_. In this group the body is elongate, covered with keeled plates imbricated like shingles. The dorsal is composed of many slender spines, and the vertebræ much elongate. In _Blochius longirostris_ (Monte Bolca Eocene) has very long jaws, lined with small teeth. Zittel regards the family as allied to the _Belonorhynchidæ_, but the prolongation of the jaws may be a character of analogy merely. Woodward places it next to the _Blenniidæ_, supposing it to have small and jugular ventral fins. But as the presence of ventral fins is uncertain, the position of the family cannot be ascertained and it may really belong in the neighborhood of _Ammodytes_. The dorsal rays are figured by Woodward as simple.

=The Patæcidæ etc.=—The _Patæcidæ_ are blenny-like fishes of Australia, having the form of _Congriopus_, the spinous dorsal being very high and inserted before the eyes, forming a crest. _Patæcus fronto_ is not rare in South Australia. The _Gnathanacanthidæ_ is another small group of peculiar blennies from the Pacific. The _Acanthoclinidæ_ are small blennies of New Zealand with numerous spines in the anal fin. _Acanthoclinus littoreus_ is the only known species.

=The Gadopsidæ, etc.=—The family of _Gadopsidæ_ of the rivers of New Zealand and southern Australia consists of a single species, _Gadopsis marmoratus_, resembling the scaly blennies called _Clinus_, but with long ventrals of a single ray, and three spines in the anal fin besides other peculiarities. The species is locally very common and with various other fishes in regions where true trout are unknown, it is called "trout."

The _Cerdalidæ_ are small band-shaped blennies of the Pacific coast of Panama. The slender dorsal spines pass gradually into soft rays. Three species are known.

The wrymouths, or _Cryptacanthodidæ_, are large blennies of the northern seas, with the mouth almost vertical and the head cuboid. The wrymouth or ghostfish, _Cryptacanthodes maculatus_, is frequently taken from Long Island northward. It is usually dusky in color, but sometimes pure white. Other genera are found in the north Pacific.

=The Wolf-fishes: Anarhichadidæ.=—The wolf-fishes (_Anarhichadidæ_) are large blennies of the northern seas, remarkable for their strong teeth. Those in front are conical canines. Those behind are coarse molars. The dorsal is high, of flexible spines. The species are large, powerful, voracious fishes, known as wolf-fishes. _Anarhichas lupus_ is the common wolf-fish of the north Atlantic, reaching a length of four to six feet, the body marked by dark cross-bands. Other similar species are found both in the north Pacific and north Atlantic. _Anarhichas lepturus_, plain brown in color, is common about the Aleutian Islands.

In the wolf-eel (_Anarrhichthys ocellatus_) of the coast of California, the head is formed as in _Anarhichas_ but the body is band-shaped, being drawn out into a very long and tapering tail. This species, which is often supposed to be a "sea-serpent," sometimes reaches a length of eight feet. It is used for food. It feeds on sea-urchins and sand-dollars (_Echinarachinius_) which it readily crushes with its tremendous teeth.

The skull of a fossil genus, _Laparus_ (_alticeps_), with a resemblance to _Anarhichas_, is recorded from the Eocene of England.

=The Eel-pouts: Zoarcidæ.=—The remaining blenny-like forms lack fin spines, agreeing in this respect with the codfishes and their allies. In all of the latter, however, the hypercoracoid is imperforate, the pseudobranchiæ are obsolete, and the tail isocercal. The forms allied to _Zoarces_ and _Ophidion_, and which we may regard as degraded blennies, have homocercal (rarely leptocercal) tails, generally but not always well-developed pseudobranchiæ and the usual foramen in the hypercoracoid.

The _Zoarcidæ_, or eel-pouts, have the body elongate, naked, or covered with small scales, the dorsal and anal of many soft rays and the gill-openings confined to the side. Most of the species live in rather deep water in the Arctic and Antarctic regions. _Zoarces viviparus_, the "mother of eels," is a common fish of the coasts of northern Europe. In the genus _Zoarces_, the last rays of the dorsal are short and stiff, like spines. The species are viviparous; the young being eel-like in form, the name "mother of eels" has naturally arisen in popular language. The American eel-pout, sometimes called mutton-fish, _Zoarces anguillaris_, is rather common north of Cape Cod, and a similar species, _Zoarces elongatus_, is found in northern Japan. _Lycodopsis pacifica_, without spines in the dorsal, replaces _Zoarces_ in California. The species of _Lycodes_, without spines in the dorsal, and with teeth on the vomer and palatines, are very abundant in the northern seas, extending into deep waters farther south. _Lycodes reticulatus_ is the most abundant of these fishes, which are valued chiefly by the Esquimaux and other Arctic races of people. Numerous related genera are recorded from deep-sea explorations, and several others occur about Tierra del Fuego. _Gymnelis_, small, naked species brightly colored, is represented by _Gymnelis viridis_ in the Arctic and by _Gymnelis pictus_ about Cape Horn.

The family of _Scytalinidæ_ contains a single species, _Scytalina cerdale_, a small snake-shaped fish which lives in wet gravel between tide-marks, on Waada Island near Cape Flattery in Washington, not having yet been found elsewhere. It dives among the wet stones with great celerity, and can only be taken by active digging.

To the family of _Congrogadidæ_ belong several species of eel-shaped blennies with soft rays only, found on the coasts of Asia. Another small family, _Derepodichthyidæ_, is represented by one species, a scaleless little fish from the shores of British Columbia.

The _Xenocephalidæ_ consist of a single peculiar species, _Xenocephalus armatus_, from the island of New Ireland. The head is very large, helmeted with bony plates and armed with spines. The body is short and slender, the ventrals with five rays, the dorsal and anal short.

=The Cusk-eels: Ophidiidæ.=—The more important family of _Ophidiidæ_, or cusk-eels, is characterized by the extremely anterior position of the ventral fins, which are inserted at the throat, each one appearing as a long forked barbel. The tail is leptocercal, attenuate, the dorsal and anal confluent around it. _Ophidion barbatum_ and _Rissola rochei_ are common in southern Europe. _Rissola marginata_ is the commonest species on our Atlantic coast, and _Chilara taylori_ in California. Other species are found farther south, and still others in deep water. _Genypterus_ contains numerous species of the south Pacific, some of which reach the length of five feet, forming a commercial substitute for cod. _Genypterus capensis_ is the klipvisch of the Cape of Good Hope, and _Genypterus australis_ the "Cloudy Bay cod" or "rock ling" of New England. Another large species, _Genypterus maculatus_, occurs in Chile. A few fragments doubtfully referred to _Ophidion_ and _Fierasfer_ occur in the Eocene and later rocks. The _Lycodapodidæ_ contain a few small, scaleless fishes (_Lycodapus_) dredged in the north Pacific.

=Sand-lances: Ammodytidæ.=—Near the _Ophidiidæ_ are placed the small family of sand-lances (_Ammodytidæ_). This family comprises small, slender, silvery fishes, of both Arctic and tropical seas, living along shore and having the habit of burying themselves in the sand under the surf in shallow water. The jaws are toothless, the body scarcely scaly and crossed by many cross-folds of skin, the many-rayed dorsal fin is without spines, and the ventral fins when present are jugular. The species of the family are very much alike. From their great abundance they have sometimes much value as food, more perhaps as bait, still more as food for salmon and other fishes, from which they escape by plunging into the sand. Sometimes a falling tide leaves a sandy beach fairly covered with living "lants" looking like a moving foam of silver. _Ammodytes tobianus_ is the sand-lance or lant of northern Europe. _Ammodytes americanus_, scarcely distinguishable, replaces it in America; and _Ammodytes personatus_ in California, Alaska, and Japan. This is a most excellent pan fish, and the Japanese, who regard little things, value it highly.

In the genus _Hyperoplus_ there is a large tooth on the vomer. In the tropical genera there is a much smaller number of vertebræ and the body is covered with ordinary scales instead of delicate, oblique cross-folds of skin. These tropical species must probably be detached from the _Ammodytidæ_ to form a distinct family, _Bleekeriidæ_. _Bleekeria kallolepis_ is found in India, _Bleekeria gilli_ is from an unknown locality, and the most primitive species of sand-lance, _Embolichthys mitsukurii_, occurs in Formosa. In this species, alone of the sand-lances, the ventral fins are retained. These are jugular in position, as in the _Zoarcidæ_, and the rays are I, 3. The discovery of this species makes it necessary to separate the _Ammodytidæ_ and _Bleekeriidæ_ widely from the _Percesoces_, and especially from the extinct families of _Crossognathidæ_ and _Cobitopsidæ_ with which its structure in other regards has led Woodward, Boulenger, and the present writer to associate it.

Although an alleged sand-lance, _Rhynchias septipinnis_, with ventral fins abdominal, was described a century ago by Pallas, no one has since seen it, and it may not exist, or, if it exists, it may belong among the _Percesoces_. The relation of _Ammodytes_ to _Embolichthys_ is too close to doubt their close relationship. According to Dr. Gill the _Ammodytidæ_ belong near the _Hemerocœtidæ_.

=The Pearlfishes: Fierasferidæ.=—In the little group of pearlfishes, called _Fierasferidæ_ or _Carapidæ_, the body is eel-shaped with a rather large head, and the vent is at the throat. Numerous species of _Fierasfer_ (_Carapus_) are found in the warm seas. These little fishes enter the cavities of sea-cucumbers (Holothurians) and other animals which offer shelter, being frequently taken from the pearl-oyster. In the Museum of Comparative Zoology, according to Professor Putnam, is "one valve of a pearl-oyster in which a specimen of _Fierasfer dubius_ is beautifully inclosed in a pearly covering deposited on it by the oyster." A photograph of a similar specimen is given above. The species found in Holothurians are transparent in texture, with a bright pearly luster. Species living among lava rocks, as _Jordanicus umbratilis_ of the south seas, are mottled black. Since this was written a specimen of this black species has been obtained from a Holothurian in Hilo, Hawaii, by Mr. H. W. Henshaw.

=The Brotulidæ.=—The _Brotulidæ_ constitute a large family of fishes, resembling codfishes, but differing in the character of the hypercoracoid, as well as in the form of the tail. The resemblance between the two groups is largely superficial. We may look upon the _Brotulidæ_ as degraded blennies, but the _Gadidæ_ have an earlier and different origin which has not yet been clearly made out. Most of the _Brotulidæ_ live in deep water and are without common name or economic relations. Two species have been landlocked in cave streams in Cuba, where they have, like other cavefishes, lost their sight, a phenomenon which richly deserves careful study, and which has been recently investigated by Dr. C. H. Eigenmann. These blind Brotulids, called Pez Ciego in Cuba, are found in different caves in the county of San Antonio, where they reach a length of about five inches. As in other blindfishes, the body is translucent and colorless. These species are known as _Lucifuga subterranea_ and _Stygicola dentata_. They are descended from allies of the genera called _Brotula_ and _Dinematichthys_. _Brotula barbata_ is a cusk-like fish, occasionally found in the markets of Havana. Similar species, _Brotula multibarbata_ and _Sirembo inermis_, are common in Japan, and _Brosmophycis marginatus_, beautifully red in color, is occasionally seen on the coast of California. Many other genera and species abound in the depths of the sea and in crevices of coral reefs, showing much variety in form and structure.

The _Bregmacerotidæ_ are small fishes, closely related to the Brotulids, having the hypercoracoid perforate, but with several minor peculiarities, the first ray of the dorsal being free and much elongate. They live near the surface in the open sea. _Bregmaceros macclellandi_ is widely diffused in the Pacific.

=Ateleopodidæ.=—The small family of _Ateleopodidæ_ includes long-bodied, deep-water fishes of the Pacific, resembling _Macrourus_, but with smooth scales. The group has the coracoids as in _Brotulidæ_, and the actinosts are united in an undivided plate. _Ateleopus japonicus_ is the species taken in Japan.

=Suborder Haplodoci.=—We may here place the peculiar family of _Batrachoididæ_, or toadfishes. It constitutes the suborder of _Haplodoci_ (ἁπλόος, simple; δόκος, shaft) from the simple form of the post-temporal. This order is characterized by the undivided post-temporal bone and by the reduction of the gill-arches to three. A second bone behind the post-temporal connects the shoulder-girdle above to the vertebral column. The coracoid bones are more or less elongate, suggesting the arm seen in pediculate fishes.

The single family has the general form of the _Cottidæ_, the body robust, with large head, large mouth, strong teeth, and short spinous dorsal fin. The shoulder-girdle and its structures differ little from the blennioid type. There are no pseudobranchiæ and the tail is homocercal. The species are relatively few, chiefly confined to the warm seas and mostly American, none being found in Europe or Asia. Some of them ascend rivers, and all are carnivorous and voracious. None are valued as food, being coarse-grained in flesh. The group is probably nearest allied to the _Trachinidæ_ or _Uranoscopidæ_.

_Opsanus tau_, the common toadfish, or oyster-fish, of our Atlantic coast, is very common in rocky places, the young clinging to stones by a sucking-disk on the belly, a structure which is early lost. It reaches a length of about fifteen inches. _Opsanus pardus_, the leopard toadfish, or sapo, of the Gulf coast, lives in deeper water and is prettily marked with dark-brown spots on a light yellowish ground.

In _Opsanus_ the body is naked and there is a large foramen, or mucous pore, in the axil of the pectoral. In the _Marcgravia cryptocentra_, a large Brazilian toadfish, this foramen is absent. In _Batrachoides_, a South American genus, the body is covered with cycloid scales. _Batrachoides surinamensis_ is a common species of the West Indies. _Batrachoides pacifici_ occurs at Panama. The genus _Porichthys_ is remarkable for the development of series of mucous pores and luminous spots in several different lateral lines which cover the body. These luminous spots are quite unlike those found in the lantern-fishes (_Myctophidæ_) and other _Iniomi_. Their structure has been worked out in detail by Dr. Charles Wilson Greene, a summary of whose conclusions are given on page 191, Vol. I.

The common midshipman, or singing fish, of the coast of California is _Porichthys notatus_. This species, named midshipman from its rows of shining spots like brass buttons, is found among rocks and kelp and makes a peculiar quivering or humming noise with its large air-bladder.

_Porichthys porosissimus_, the bagre sapo, is common on all coasts of the Gulf of Mexico and the Caribbean Sea. _Porichthys margaritatus_ is found about Panama and _Porichthys porosus_ in Chile.

The species of _Thalassophryne_ and _Thalassothia_, the poison toadfishes, are found along the coasts of South America, where they sometimes ascend the rivers. In these species there is an elaborate series of venom glands connected with the hollow spines of the opercle and the dorsal spines. Dr. Günther gives the following account of this structure as shown in _Thalassophryne reticulata_, a species from Panama:

"In this species I first observed and closely examined the poison organ with which the fishes of this genus are provided. Its structure is as follows: (1) The opercular part: The operculum is very narrow, vertically styliform and very mobile; it is armed behind with a spine, eight lines long in a specimen of 10½ inches, and of the same form as the venom fang of a snake; it is, however, somewhat less curved, being only slightly bent upward. It has a longish slit at the outer side of its extremity which leads into a canal perfectly closed and running along the whole length of its interior; a bristle introduced into the canal reappears through another opening at the base of the spine, entering into a sac situated on the opercle and along the basal half of the spine; the sac is of an oblong-ovate shape and about double the size of an oat grain. Though the specimen had been preserved in spirits for about nine months it still contained a whitish substance of the consistency of thick cream, which on the slightest pressure freely flowed from the opening in the extremity of the spine. On the other hand, the sac could be easily filled with air or fluid from the foramen of the spine. No gland could be discovered in the immediate neighborhood of the sac; but on a more careful inspection I found a minute tube floating free in the sac, whilst on the left-hand side there is only a small opening instead of the tube. The attempts to introduce a bristle into this opening for any distance failed, as it appears to lead into the interior of the basal portion of the operculum, to which the sac firmly adheres at this spot. (2) The dorsal part is composed of the two dorsal spines, each of which is ten lines long. The whole arrangement is the same as in the opercular spines; their slit is at the front side of the point; each has a separate sac, which occupies the front of the basal portion; the contents were the same as in the opercular sacs, but in somewhat greater quantity. A strong branch of the lateral line ascends to the immediate neighborhood of their base. Thus we have four poison spines, each with a sac at its base; the walls of the sacs are thin, composed of a fibrous membrane, the interior of which is coated over with mucus. There are no secretory glands embedded between these membranes, and these sacs are probably merely the reservoirs in which the fluid secreted accumulates. The absence of a secretory organ in the immediate neighborhood of the reservoirs (an organ the size of which would be in accordance with the quantity of fluid secreted), the diversity of the osseous spines which have been modified into poison organs, and the actual communication indicated by the foramen in the sac lead me to the opinion that the organ of secretion is either that system of muciferous channels which is found in nearly the whole class of fishes, and the secretion of which has poisonous qualities in a few of them, or at least an independent portion of it. This description was made from the first example; through the kindness of Captain Dow I received two other specimens, and in the hope of proving the connection of the poison bags with the lateral-line system, I asked Dr. Pettigrew, of the Royal College of Surgeons, a gentleman whose great skill has enriched that collection with a series of the most admirable anatomical preparations, to lend me his assistance in injecting the canals. The injection of the bags through the opening of the spine was easily accomplished; but we failed to drive the fluid beyond the bag or to fill with it any other part of the system of muciferous channels. This, however, does not disprove the connection of the poison bags with that system, inasmuch as it became apparent that if there be minute openings they are so contracted by the action of the spirit in which the specimens were preserved as to be impassable to the fluid of injection. A great part of the lateral-line system consists of open canals; however, on some parts of the body, these canals are entirely covered by the skin; thus, for instance, the open lateral line ceases apparently in the suprascapular region, being continued in the parietal region. We could not discover any trace of an opening by which the open canal leads to below the skin; yet we could distinctly trace the existence of the continuation of the canal by a depressed line, so that it is quite evident that such openings do exist, although they may be passable only in fresh specimens. Thus likewise the existence of openings in the bags, as I believed to have found in the first specimen dissected, may be proved by examination of fresh examples. The sacs are without an external muscular layer and situated immediately below the loose thick skin which envelops their spines to their extremity. The injection of the poison into a living animal, therefore, can only be effected by the pressure to which the sac is subjected the moment the spine enters another body. Nobody will suppose that a complicated apparatus like the one described can be intended for conveying an innocuous substance, and therefore I have not hesitated to designate it as poisonous; and, Captain Dow informs me in a letter lately received, 'the natives of Panama seemed quite familiar with the existence of the spines and of the emission from them of a poison which, when introduced into a wound, caused fever, an effect somewhat similar to that produced by the sting of a scorpion; but in no case was a wound caused by one of them known to result seriously. The slightest pressure of the finger at the base of the spine caused the poison to jet a foot or more from the opening of the spine.' The greatest importance must be attached to this fact, inasmuch as it assists us in our inquiries into the nature of the functions of the muciferous system, the idea of its being a secretory organ having lately been superseded by the notion that it serves merely as a stratum for the distribution of peripheric nerves. Also the objection that the sting-rays and many Siluroid fishes are not poisonous because they have no poison organ cannot be maintained, although the organs conveying their poison are neither so well adapted for this purpose nor in such a perfect connection with the secretory mucous system as in _Thalassophryne_. The poison organ serves merely as a weapon of defense. All the Batrachoids with obtuse teeth on the palate and in the lower jaw feed on Mollusca and Crustaceans."

No fossil _Batrachoididæ_ are known.

=Suborder Xenopterygii.=—The clingfishes, forming the suborder _Xenopterygii_ (ξενός, strange; πτερύξ, fin), are, perhaps, allied to the toadfishes. The ventral fins are jugular, the rays I, 4 or I, 5, and between them is developed an elaborate sucking-disk, not derived from modified fins, but from folds of the skin and underlying muscles.

The structure of this disk in _Gobiesox sanguineus_ is thus described by Dr. Günther:

"The whole disk is exceedingly large, subcircular, longer than broad, its length being (often) one-third of the whole length of the fish. The central portion is formed merely by skin, which is separated from the pelvic or pubic bones by several layers of muscles. The peripheric portion is divided into an anterior and posterior part by a deep notch behind the ventrals. The anterior peripheric portion is formed by the ventral rays, the membrane between them and a broad fringe which extends anteriorly from one ventral to the other. This fringe is a fold of the skin, containing on one side the rudimentary ventral spine, but no cartilage. The posterior peripheric portion is suspended on each side on the coracoid, the upper bone of which is exceedingly broad, becoming a free, movable plate behind the pectoral. The lower bone of the coracoid is of a triangular form, and supports a very broad fold of the skin, extending from one side to the other, and containing a cartilage which runs through the whole of that fold. Fine processes of the cartilage are continued into the soft striated margin, in which the disk terminates posteriorly. The face of the disk is coated with a thick epidermis, like the sole of the foot in higher animals. The epidermis is divided into many polygonal plates. There are no such plates between the roots of the ventral fins."

The body is formed much as in the toadfishes. The skin is naked and there is no spinous dorsal fin. The skeleton shows several peculiarities; there is no suborbital ring, the palatine arcade is reduced, as are the gill-arches, the opercle is reduced to a spine-like projection, and the vertebræ are numerous. The species are found in tide-pools in the warm seas, where they cling tightly to the rocks with their large ventral disks.

Several species of _Lepadogaster_ and _Mirbelia_ are found in the Mediterranean. _Lepadogaster gouani_ is the best-known European species. _Aspasma ciconiæ_ and _minima_ occur about the rocks in the bays of Japan.

Most of the West Indian species belong to _Gobiesox_, with entire teeth, and to _Arbaciosa_, with serrated teeth. Some of these species are deep crimson in color, but most of them are dull olive. _Gobiesox virgatulus_ is common on the Gulf Coast. _Caularchus mæandricus_, a very large species, reaching a length of six inches, abounds along the coast of California. Other genera are found at the Cape of Good Hope, especially about New Zealand. _Chorisochismus dentex_, from the Cape of Good Hope, reaches the length of a foot.