THE STATE GEOLOGIST. 95 



to Newberry)-, which are too imperfectly preserved for satis- 

 factory determination or definition. They have been obtained 

 from but a single locality, in rather coarse sandy shales near 

 Chicopee Falls, Mass., which have been considerably metamor- 

 phosed by igneous agencies. This circumstance, as stated by 

 Newberry, "has obscured some of the details of structure, such 

 as the surface of the scales, the shape and markings of the head- 

 bones, etc., but has left the outlines of the body and the position 

 and form of the fins distinctly visible. The most striking char- 

 acters of these fishes are the narrow wedge-shaped form of body, 

 the straightness of the dorsal and ventral lines, the smallness 

 of the fins, the posterior position of the dorsal, and the rounded 

 and unarmed margins of the median dorsal scales." Assuming 

 the correctness of the generic determination, this is the only 

 species of Acentrophorus which has yet been recognized in this 

 country. 



Family CATOPTERID^. 



Genus Catopterus Redfield (Redfieldius Hay). 



Trunk elegantly fusiform, head relatively small, tail hemi- 

 heterocercal. External bones more or less ornamented with 

 ridges and tubercles of ganoine; no median series of cranial roof 

 bones. Fins of moderate size, consisting of robust rays, more 

 or less enameled, and distally bifurcated; fulcra well developed, 

 short and closely set. Dorsal and anal fins triangular, the 

 origin of the former behind that of the latter ; caudal fin forked. 

 Scales large or of moderate size, nearly or quite smooth, and 

 serrated along their postero-inferior margin; dorsal ridge-scales 

 not much enlarged. Teeth numerous, small, acutely conical. 



This is an exclusively American genus, although a closely 

 allied form, Dictyopyge, occurs in both Europe and America. 

 These two genera constitute a family by themselves, Catopteridcs, 

 which is evidently descended from the ancient PalcEoniscidce, the 

 group from which modern sturgeons and paddle-fishes are 

 also derived. The structure of the head and shoulder-girdle has 

 not yet been worked out for these two Triassic genera, but they 



