M. Length of neck to point between coracoid and precoracoid ·0345 Length of coracoid (about) ·133 Length of precoracoid ·114 Length of scapula (about) ·126 BAENA, Leidy. Baena undata, Leidy. Cont. to Ex. Vert. Fauna, p. 160. Three nearly perfect shells of different ages, from Dry and Cottonwood Creeks. TRIONYX, Geoffr. Trionyx uintaensis, Leidy. Cont. to Ex. Vert. Fauna, p 176. Cottonwood Creek. PISCES. TELEOSTEI. TELEOCEPHALI. _CYPRINODONTIDÆ._ "Head and body covered with scales; barbels, none. Margin of the upper jaw formed by the premaxillaries only. Teeth in both jaws; upper and lower pharyngeals, with cardiform teeth. Dorsal fin situated on the hinder half of the body." (Günther.) TRICOPHANES, Cope. U. S. Geolog. Surveyor the Terrs., 1872, p. 641. Having secured a very perfect specimen of this genus, we are enabled to complete the definition of its generic characters. We give, then, Professor Cope's definition, with some emendations and additions: Dorsal and anal fins short; ventral fin sometimes beneath and sometimes in advance of the dorsal. The premaxillary forms all of the superior arcade of the mouth, which has a wide gape, opening back behind the orbit. This bone has a row of long, slender, recurved, and subequal teeth implanted in it. The dentary is stout, and has a few small teeth. The branchiostegal rays are six in number, and are rather wide. The preoperculum IS serrate. The operculum is ridged on top. The anterior vertebræ are unmodified, and the centra are not elongate. A strong acute spine supports the dorsal, and a similar one the anal fin. There is a long post-clavicle, which may or may not extend to the base of the ventral parallel with the femur. The femur is long and furcate; the external part straight and reaching to the clavicle; the internal curves to meet the corresponding portion of its fellow. The ventral radii are eight in number, and the caudal fin is furcate. The scales are peculiar, and characteristic of the genus. They are very thin, and have borders fringed with long, close-set, bristle-like processes. This genus includes as yet only three species: _T. hians_, from Osivio, Nev.; and _T. foliarum_ and _T. Copei_, from Florissant, Col. Tricophanes Copei, _sp. nov._