50 ON A GENUS AND SPECIES OF 



cgonus ; the body is deep and moderately thick, strongly 

 arched behind the head and rounded on the belly. The 

 head is rather small, about one-sixth of the total length, 

 including the caudal fin, or a little more than half of the 

 depth ; it is quite naked and approaches the subconical in 

 its outlines, but is blunt and rounded on the snout; across 

 the interorbital space it is strongly arched. Snout broad, 

 nearly twice as long as the orbit, rounded. Nostrils close 

 together, separated by a valvular fold of the skin ; poste- 

 rior larger, subtriangular ; anterior much smaller, circu- 

 lar, nearer to the eye than to the end of the snout. The 

 orbit measures about one-fifth of the length of the head, 

 or two-fifths of the interorbital space. Mouth wide, ex- 

 tending almost as far back as the middle of the eye, with- 

 out an upper lip, with a well developed lower lip. 



Teeth broad, compressed to a sharp edge, which is 

 rounded on the summit. At each side of the rounded or 

 spatulate cutting portion of each tooth, near its base, 

 there are two small denticles or cusps, the upper of which 

 is the sharper. As the teeth are imbricated in the series, 

 in such a way that the outer (hinder) edge of each lies 

 outside of the next following, only the posterior pair of 

 the denticles of a tooth are visible from without, the ante- 

 rior pair being hidden by the tooth immediately. preceding 

 in the row. On mandibles, intermaxillaries and maxilla- 

 ries the teeth are alike. Those on the latter occupy more 

 than the half of its length and extend almost to a vertical 

 from the middle of the eye ; they with those of the inter- 

 maxillary form a continuous and regular series. On the 

 intermaxillary close behind the middle, there is a short se- 

 ries of three (four) smaller teeth of similar shape. The 

 maxillary is firmly connected with the intermaxillary and 

 at the hinder end of the dental series becomes narrower and 

 bends downward abruptly. At the symphysis behind the 



