The singular and powerfully developed dental system of the Wolf-fish (Anarrhi ehas Lupus) has been a subject of interest to many anatomists. The general character and physiological relations of the teeth in this species had not escaped the attention of Hunter. In his paper on the Gillaroo trout, read before the Royal Society in 1774, he ob serves that " the teeth of fishes which subsist chiefly on animal matter must vary according as their food may be common salt fish, or shell-fish." " Such fish as live on the first kind have, like the carnivorous quadrupeds and birds, no apparatus for mastication, their teeth being intended merely for catching the food and fitting it to be swallowed. But the shells of the second kind of food render some de gree of masticatory power necessary to fit it for its passage either into the stomach or through the intestines : and accordingly we find in certain fish a structure suited to the purpose. Thus the mouth of the Wolf-fish is almost paved with teeth, by means of which it can break shells to pieces, and fit them for the oesophagus of the fish, and so effectually disengage the food from them, that though it lives upon such hard food, the stomach does not differ from that of other fish." But in order to secure the capture of the shell-fish, the teeth of the Wolf-fish are not all crushers ; some present the laniary type, with the apices more or less recurved and blunted by use, and consist of strong cones spread abroad, like grappling hooks, at the anterior part of the mouth.* The premaxillary teeth are all conical, and arranged in two rows ; there are two, three, or four in the exterior row, at the mesial half of the bone, which are the largest ; and from six to eight smaller teeth are irregularly arranged behind. There are three large, strong, diverging laniaries at the anterior end of each premandibular bone, and immediately behind these an irregular number of shorter and smaller conical teeth, which gradually exchange this font for that of large obtuse tubercles ; these extend backwards, in a double alternate series, along a great part of the alveolar border of the bone, and are termi nated by two or three smaller teeth in a single row, the last of which again presents the conical form. Each palatine bone supports a double row of teeth, the outer ones being conical and straight, and from four to six in number ; the inner ones two, three, or four in number, and tuberculate. I have seen a spe cimen where the inner row was wanting on one side. The lower surface of the vomer is covered by a double irregularly alternate series of the same kind of large tuberculate crushing teeth as those at the middle of the premaudibular. All the teeth are anchylosed to more or less developed alveolar eminences, like the anterior teeth of the Lophius. The periphery of the expanded circular base of the large anterior grappling teeth is divided into processes indicative of the original ligamen tous fasciculi at the base of the pulp by the ossification of which their anchylosis is ef fected.
When such anchylosed teeth and the sup porting bone are divided by a vertical sec tion, as in fig. 2, pl. 66, of my " Odonto graphy," there may be generally discerned a faint transverse line indicating the original separation between the tooth and the bone, and more clearly defining the dental from the osseous structure, than in the anchylosed teeth of other fishes. From the enormous develop ment of the muscles of the jaws, and the strength of the shells of the whelks and other testacea which are cracked and crushed by the teeth, their fracture and displacement must obviously be no unfrequent occurrence ; and most speci mens of the jaws of the Wolf-fish exhibit some of the teeth either separated at this line of imperfect anchylosis, or, more rarely, broken off above the base, or, still more rarely, de tached by fracture of the supporting osseous alveolar process.
With regard to the substance of the teeth of fishes, the modifications of dentine, called vaso-dentine and osteo-dentine *, predomi nate much more than in the higher Verte brate; and they thus more closely resemble the bones which support them. There is, however, great diversity in respect of sub stance. The teeth of most of the Chmto donts are flexible, elastic, and composed of a yellowish subtransparent albuminous tissue ; such, likewise, are the labial teeth of the He lostome, the premaxillary and mandibular teeth of the Goniodonts, and of that percoid genus thence called Trichodon. In the Cy
clostomes the teeth consist of a denser albu minous substance. The upper pharyngeal molar of the Carp consists of a peculiar brown and semitransparent tissue, hardened by salts of lime and magnesia. The teeth of the Fly ing-fish (Exoccetus), and Sucking-fish (Re mora), consist of osteo-dentine. In many fishes, e.g. the Acanthurus, Sphyrama, and certain Sharks (Lamna, fig. 545.), a base, or body of osteo-dentine is coated by a layer of true dentine, but of unusual hardness, like enamel : in Prionodon this hard tissue predo minates. In the Labrus the pharyngeal crush ing teeth consist wholly of hard or unvascular dentine (fig. 544.). In most Pycnodonts and Cestracionts, and many other fishes, the body of the tooth consists of ordinary unvascular dentine, covered by a modification of that tissue which I have called "vitro-dentine" from its clear, polished, enamel-like character : but this is not enamel, nor the product of a dis tinct organ from the dentinal pulp : it differs from ordinary dentine in the greater propor tion of the mineral particles, their more mi nute diffusion through the gelatinous basis, in the straighter course and more minute size of the calcigerous tribes ; it results from the calcification of the external layer of the den tinal pulp, and is the first part of the tooth which is formed. In Sargus and Balistes the body of the tooth consists of true dentine, and the crown is covered by a thick layer of a denser tissue, developed by a distinct organ, and differing from the " enamel " of higher animals only in the more complicated and or ganised mode of deposition of the earthy salts. The ossification of the capsule of the complex matrix of these teeth covers the enamel with a thin coating of "cement." In the pharyngeal teeth of the Scares a fourth substance is added by the ossification of the base of the pulp after its summit and periphery have been converted into hard dentine ; and the teeth (fig. 558.), thus composed of cement (c), enamel (e), dentine (d), and osteo-dentine, are the most complex in regard to their sub stance that have yet been discovered in the animal kingdom.
The tubes which convey the capillary ves sels through the substance of the osteo- and vaso-dentine of the teeth of fishes* were early recognised, on account of their com paratively large size ; as by Andre, e.g. in the teeth of Acanthurus, and by Cuvier and Von Born in the teeth of the Wolf-fish and other species. Leeuwenhoek had also detected the much finer tubes of the peripheral dentine of the teeth of the Haddock. These " den tinal tubuli" are given off from the parietes of the vascular canals, and bend, divide, and subdivide rapidly in the hard basis-tissue of the interspaces of those canals in osteo-den tine ; the dentinal tubuli alone are found in true dentine, and they have a straighter and more parallel course, usually at right angles to the outer surface of the dentine. Those conical teeth which, when fully formed, con sist wholly or in great part of osteo-den tine or vaso-dentine, always first appear with an apex of hard or true dentine. In some fishes the simple central basal pulp-cavity of such teeth, instead of breaking up into irregu _ar or parallel canals, sends out a series of vertical plates from its periphery, which, when calcified, give a fluted character to the base of the tooth, e. g. in Lepidosteus aryurus.f Sometimes such radiating vertical basal plates of dentine are wavy in their course, and send off narrow processes from their sides; and, as a thin layer of the outer capsule interdigi tates with the outstanding plates of the den tinal pulp, and becomes co-calcified with them, a transverse section of such a tooth presents a series of interblended wavy or labyrinthic tracts of thick dentine radiating from the cen tre, and of thin cement converging towards the centre of the tooth.t An analogous but more complicated structure obtains when the ra diating, wavy, vertical plates of dentine dicho tomise, and give off from their sides, through out their course, numerous branch plates and processes, which are traversed by medullary sinuses and canals with their peripheral ter minations dilated, and becoming the centres of lobes or columns of hard dentine. The transverse section of such teeth gives the ap pearance of branches of a tree, with leaf-stalks and leaves, radiating from the central pulp cavity to the circumference of the tooth ; and I have called the fossil fish in which this structure was first detected, Dendrodus.