The _Semionotidæ_ (_Stylodontidæ_) are robust-bodied Ganoids, having the vertebræ developed as rings, the jaws with several rows of teeth, those of the outer row styliform. _Semionotus bergeri_ is a well-known species, with the body moderately elongate. _Semionotus agassizi_ and many other species occur in the Triassic of the Connecticut valley and in New Jersey. The body is very deep in the related genus _Dapedium_, and the head is covered with strong bony plates. _Dapedium politum_ is a well-known species of the English Triassic. _Tetragonolepis_ (_Pleurolepis_) is a similar form, very deep and compressed, with strong, firm scales. In the extinct family of _Lepidotidæ_ the teeth are conical or chisel-shaped, while blunt or molar teeth are on the inside of the mouth, which is small, and the suspensorium of the mandible is vertical or inclined forward. The body is robust-fusiform, covered with rhomboid scales; the vertebræ form rings about the notochord; the teeth are either sharp or blunt. The dorsal fin is short, with large fulcra. The best known of the numerous genera are _Lepidotes_, rather elongate in body, with large, blunt teeth. Of the many species of _Lepidotes_, _Lepidotes elvensis_ abounds in the English and German Triassic, and _Lepidotes minor_ in the English Triassic. Another well-known European species is _Lepidotes mantelli_. [Illustration: FIG. 15.—_Dapedium politum_ Leach, restored. Family _Semionotidæ_. (After Woodward.) ] The _Isopholidæ_ (_Eugnathidæ_) differ from the families last named in the large pike-like mouth with strong teeth. The mandibular suspensorium is inclined backwards. The body is elongate, the vertebræ forming incomplete rings; the dorsal fin is short with large fulcra. _Isopholis dentosus_ is found with numerous other species in the British Triassic. _Caturus furcatus_ is especially characteristic of Triassic rocks in Germany. _Ptycholepis marshi_ occurs in the Connecticut valley. [Illustration: FIG. 16.—_Tetragonolepis semicinctus_ Brown. Lias. Family _Semionotidæ_. (After Woodward.) ] The _Macrosemiidæ_ are elongate fishes with long dorsal fin, the numerous species being found in the Triassic, Jurassic, and Cretaceous of Europe. _Macrosemius rostratus_ has a very high, continuous dorsal. _Macropistius arenatus_ is found in the Cretaceous of Texas, the only American species known. Prominent European genera are _Notagogus_, _Ophiopsis_, and _Petalopteryx_. [Illustration: FIG. 17.—_Isopholis orthostomus_ (Agassiz). Lias. (After Woodward.) ] [Illustration: FIG. 18.—The Long-nosed Garpike, _Lepisosteus osseus_ (Linnæus). Fox River, Wisconsin. (From nature; D. S. Jordan and M. L. McDonald, 1874.) ]