474 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 
membrane at the opercular margin; 1.4 to 1.7 times in the snout. 
The least interorbital width is located above the front of the pupil, 
and is contained 1.5 to 1.8 times in the postorbital; the least sub- 
orbital width, 2.6 to 2.7. The upper jaw extends backward almost - 
or quite to the vertical below the hind margin of the pupil, and 
is contained from 3.95 to 4.8 times in the head. Bands of fine teeth 
occur in the jaws; the outermost premaxillary series 1s somewhat en- 
larged. Barbel, 4.0 to 7.0 in postorbital length of head. Six branchi- 
ostegals; the gill-membranes have a free fold of variable width. 
The center of the anus les in advance of the origin of the anal 
fin a distance half to two-thirds that between the anus and the base 
of the outer ventral ray; the distance from anus to ventral is con- 
tained 1.25 to 1.5 times in the distance from the ventral to the 
isthmus, or in the postorbital length of the head. No trace of a 
scaleless ventral fossa can be found in specimens in which no scales 
are lost, but the scales are often fallen in an area before the anus. A 
gland-like body extends forward from the peritroct to between the 
ventrals, above the position occupied by the ventral fossa in those 
species in which the fossa is present; this organ is slender posteriorly, 
but widens anteriorly to an ellipsoidal form; its ventral surface is 
black, in strong contrast to its silvery dorsal face. 
The scales are léss closely imbricate than in C. dorsalis; they are 
constantly in 54 rows between the lateral line and the origin of the 
second dorsal. The scales of the body are moderately rough, being 
more strongly spinose than in (. dorsalis. Each scale is armed with 
5 to 10 well-formed, slightly divergent spinous carinae. The spinules 
are fewer than nine on each carina; they increase in size posteriorly 
on each carina, the last one projecting beyond the scale margin. The 
ridges of the head are rendered quite rough by scales armed with 
several carinae. Six or seven scales cover the ethmoid, and 9 to 11 
the preorbital portion of the infraorbital ridge. The dorsoterminal 
plate is of variable length and breadth, and is nearly smooth medi- 
ally; the ventroterminal plate is rough with conic spines. 
The median rostral ridge is covered by seven to nine oblong- 
elliptical scales, on which the carinae radiate in all directions from 
a point near the center of the anterior scales, but from a point near 
the front margin of the posterior ones. The inner oblique group of 
carinae are obsolescent on those scales which form the series bound- 
ing the median rostral series. The character of the squamation be- 
tween the occipital ridges in diagnostic of the species: from the end 
of the median rostral ridge backward for a distance equal to the 
vertical diameter of the orbit, the scales are similar to those of the 
body, but are rather smaller, and are arranged in five irregular rows; 
behind these there abruptly follows an area in which the scales are 
much reduced in size and armature; this area is followed by a cres- 
