286 
U. S. P. R. R EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
extremity does not reacli the insertion of the ventrals in the female, whilst in the male they 
extend beyond. 
D 1, 9 ; A 1, 9 ; C 8, 1, 8, 8, 1, 7 ; V 1, 9 ; P 15. 
The scales are quite diversified, being of different sizes, according to the regions of the body. 
They are very small on the dorsal region between the occiput and the dorsal fin, increasing 
somewhat in size between the dorsal and the caudal, and becoming almost uniform along the 
peduncle of the tail. They are largest along the flanks, whilst they are again reduced in size 
on the belly from the throat to the anal fin. In shape they are sub-elliptical, anteriorly 
truncated, or undulated, longer than deep, exhibiting radiating furrows, not only upon the 
posterior section, but likewise laterally. The lateral line is very conspicuous, slightly deflexed 
along the flanks, where it is equidistant between the dorsal and abdominal outlines, to the 
very base of the caudal fin. 
The color is uniformly greyish brown above and yellowish beneath. The fins assuming the 
tints of the region of the body to which they belong. 
List of specimens. 
Catal. 
No. 
Cor. No. 
of teeth. 
No. of 
spec. 
Age. 
Locality. 
When 
collected. 
Whence obtained. 
Nature of Collected by— 
specimen, j 
246 
2798 
3 
Adult. 
1852 
Capt. L. Sitgreaves... 
Alcoholic.. Dr.S.W.Woodhouse. 
2. GILA ELEGANS, B. & G. 
Spec. Char. —Body very slender ; tail very much attenuated. Head constituting the fifth of the total length. Eye small, 
sub-elliptical ; its diameter entering seven times in the length. Posterior extremity of maxillar bone extending to a vertical 
line drawn in advance of the orbit. Anterior margin of dorsal fin nearer the extremity of the snout than the base of the caudal. 
Base of anal fin entering about nine times in the total length. Origin of ventrals much nearer the extremity of the snout than 
the base of the caudal. Reddish brown above ; metallic yellow beneath. 
Syn —Gila elegans, B. & G. in Proc. Acad. Nat. Sc. Philad. VI, 1853, 369 ; and, in Sitgr. Rep. Zunii and Color. Rivers, 
1853, 150, pi. ii.— Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 205. 
The most striking peculiarity of this species consists in its elongated and slender body, and 
especially its slender tail, terminated by a rather well developed and deeply furcated caudal fin. 
Indeed, all the fins are proportionally well developed. The greatest depth in advance of the 
dorsal enters seven times in the total length. The greatest thickness being about the half of the 
depth. 
The head is very much depressed, flattened upon the snout, forming the fifth of the total 
length. The eyes are sub-elliptical, their diameter entering seven times in the length of the 
side of the head, and twice between the tip of the snout and the anterior rim of the orbit. 
They are more apparent upon a view of the head from beneath than from above. The nostrils 
are situated entirely upon the upper surface of the snout, further apart from the extremity of 
the latter than the eye. The mouth is inferior ; the upper jaw overlapping the lower. The 
posterior extremity of the maxillar bone extending to a vertical line drawn in advance of the 
orbit. The isthmus is very small. 
The rays in all the fins have the same general structure as in the preceding species ; the 
dorsal and anal are provided anteriorly with three rudimentary rays instead of one, and the pos¬ 
terior margins of either of these fins is much lower than the anterior margin as compared to the 
