50 ON A GENUS AND SPECIES OF 
egonus ; the body is deep iiiid 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-tifth 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 ot 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 inmiediately preceding 
in the row. On mandibles, intermaxillaries and maxilla- 
ries the teeth are alike. Those on the latter occui)y 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 comiected with the intermaxillary and 
at the hinder end of the dental series becomes narrower and 
bends downward abruptly. At the symphysis behind the 
