As regards texture the teeth of fishes show considerable variation. The conical teeth of the Cyclostomes and the setiform teeth of many Teleosteans consist of a horny albuminous substance. The principal substance of the teeth of other fishes consists of dentine, with numerous dividing and anastomosing tubercles, sometimes covered by a stratum of unvascular dentine. An enamel-like substance has been observed on the crown of the teeth of _Sargus_ and _Balistes_, and an ossification of the capsule of their matrix covers the enamel with a thin coating of cement. The teeth either possess a cavity in which the matrix is received, or, more frequently, they are solid, in which case vascular canals of the underlying bone are continued into the substance of the tooth. In the teeth of some fishes numerous sets of canals and tubes are so arranged that they do not anastomose with one another, each set being surrounded by a layer of dentine and cement. These apparently simple teeth are evidently composed of numerous small teeth, and called _compound_ teeth. The teeth may be, and generally are, very different as regards size or form in the different parts of the mouth; they may be also different according to the age or sex of the fish (_Raja_). The teeth may be few in number and _isolated_, or placed in a single, double, or triple _series_, _distant_ from one another or _closely set_; they may form narrow or broad _bands_, or _patches_ of various forms. As regards form, they may be cylindrical or conical, pointed, straight, or curved, with or without an angular bent near their base; some are compressed laterally or from the front backwards; the latter may be triangular in shape, or truncated at the top like incisors of mammals; they may have one apex (cusp) only, or be bi- or tri-lobate (bi- or tri-cuspid); or have the margins denticulated or serrated. Compressed teeth may be confluent, and form a cutting edge in both jaws, which assume the shape of a parrot’s beak (Fig. 53). In some the apex is hooked or provided with barbs. Again, some teeth are broad, with flat or convex surface, like molar teeth. With regard to size, the finest teeth are like fine flexible bristles, _ciliiform_ or _setiform_; or, if very short and anchylosed to the bone, they appear only as inconspicuous asperities of the bone. Very fine conical teeth arranged in a band are termed _villiform_ teeth; when they are coarser, or mixed with coarser teeth, they are _card-like_ (dents en rape or en cardes) (Fig. 54); molar-like teeth of very small size are termed _granular_. [Illustration: Fig. 53.--Jaws of Calliodon.]