Vertebræ D. 12, C. 18, Radii D. 14, A. 8, V. 8, C. 41, P. 5 only visible, not all preserved. The dorsal fin is long, and projects beyond the beginning of the anal fin; the mouth is terminal, and the muzzle rather sharp. All the bones of the skeleton are very slender; and this is especially true of the ribs, which are not as thick as the interneurals. The neural and hæmal spines are short and slender. The origin of the dorsal is nearer to the muzzle than to the caudal; though, as a whole, the fin is on the hinder half of the body. There are no interneural spines in front of the dorsal fin; those supporting the fin are short, slender, and without the laminar expansions found in _T. foliarum_. The caudal fin consists of numerous jointed rays, which are supported by the neural and hæmal spines of the last three vertebræ. The scales are small, and exhibit the peculiarities of the genus, but the rows are too imperfect to be counted. _Measurements._ M. Total length (straight) ·0935 Length of head ·018 Length of vertebral column ·055 Length of caudal fin ·024 Length of dorsal spine ·011 Length of anal spine ·009 Depth of head posteriorly ·016 Length of mandibular ramus ·010 Length to dorsal fin (from muzzle) ·033 Length of dorsal fin ·0135 Depth of body at middle of dorsal fin ·017 Found in the insect beds at Florissant, Col. _CATOSTOMIDÆ._ Body covered with scales; head naked; margin of upper jaw formed by the premaxillaries; mouth toothless. Pharyngeal teeth in a single series, and exceedingly numerous and closely set. Dorsal fin elongate and opposite the ventrals. Anal short, or of moderate length. AMYZON, Cope. U. S. Geolog. Survey of the Terrs., 1872, p. 642. Allied to _Bubalichthys_. Dorsal fin elongate, with a few fulcral spines in front. There are three broad branchiostegals. The vertebræ are short, and the hæmal spines of the caudal fin are distinct and rather narrow. The teeth are arranged comb-like, are truncate, and number from thirty to forty. The dentary bone is slender and toothless, and the angular is distinct. Amyzon commune, Cope. U. S. Geolog. Survey of Terrs., 1873, p. Represented by several fine specimens from near Castello's Ranch, Col. _SAURODONTIDÆ._ For a very complete definition of this family, see Cope's Cretac. Vert., p. 183. PORTHEUS, Cope. Cretac. Vert., p. 189 et seq.