"Teeth subcylindric, without serrate or cutting edges, occupying the maxillary, premaxillary, and dentary bones; size, irregular; premaxillary, median maxillary, and dentary much reduced. No foramina on inner face of jaws. Teeth on the premaxillary reduced in number. Opercular and pre-opercular bones very thin. Cranial bones not sculptured." Portheus thaumas (?), Cope. Loc. cit. p. 196. Maxillary large, teeth three; third mandibular small, without cross groove in front of it. A single tooth from the cretaceous sandstone of Cement Gulch, Col., is provisionally referred to this species; the reference cannot be certain, as the specimens described and figured by Professor Cope have the crowns of the teeth broken. The tooth is not so long as the largest tooth of _P. molossus_, but is of proportionately greater diameter and not so straight. It is conical and recurved, and shows two very obscure cutting-edges, which divide the crown into two unequal faces. It has faint longitudinal striations on all sides, and the apex is sharp. _Measurements._ M. Fore-and-aft diameter at the base 0·613 Height of crown 0·020 NEMATOGNATHI. _SILURIDÆ._ "Skin naked, or with osseous scutes, but without scales. Barbels always present; maxillary bone rudimentary, margin of the upper jaw formed by the premaxillaries only. Suboperculum absent; adipose fin present or absent." (Günther.) RHINEASTES, Cope. U. S. Geol. Survey of the Terrs., 1872, p. 638. A genus allied to the recent _Ichtælurus_ but differing in the inferior grooving of the vertebræ and in the rough exostoses of the cranial bones. It differs from _Phareodon_ in having the usual band of bristle-like teeth on the dentary. Rhineastes ---- ? Represented by a portion of the dentary and hyomandibular bones of a large cat-fish from Bridger Butte. The dentary is broad and shallow, grooved below, and deeply striated on the external face. As much of it as is preserved is straight. The teeth are small, subequal throughout, and very numerous. The hyomandibular is broad and thick, and has a striated surface. The condyle is peculiar in having two separate articular faces above and below, one convex and the other flat. GANOIDEI. CYCLOGANOIDEI. _AMIIDÆ._ "Scales cycloid; a long, soft dorsal fin. Abdominal and caudal parts of the vertebral column subequal in extent." (Günther.) AMIA. Body elongate sub-cylindrical, compressed behind; snout short and rounded. Jaws with an outer series of closely-set pointed teeth, and with a band of small teeth, similar teeth on the vomer, palatine, and pterygoid bones. Long dorsal, short anal, and rounded nonfurcate caudal fin. Ventrals well developed. A single large gular plate; branchiostegal rays ten to twelve. Amia (Protamia) uintaensis, Leidy. Cont. to Ext. Vert. Fauna, p. 185.