288 
U. S. P. R. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
is a little higher than long, with its upper margin slightly concave. The anal fin resembles 
the dorsal in form and proportions, being slightly convex exteriorly and deeper than long. Its 
anterior margin is situated a little backwards to the posterior margin of the dorsal. The caudal 
is deeply furcated ; its lobes being symmetrical. The developed rays of these three fins are 
bifurcated twice upon their length. The ventrals are suh-oval; their insertion is placed some¬ 
what in advance of the dorsal, and when bent backwards their tip reaches the vent and 
occasionally also the anterior margin of the anal fin. The pectorals are sub-triangular, 
tapering ; their insertion is close to the head, rather more towards the inferior aspect than on 
the sides ; their extremity does not reach the insertion of the ventrals, and consequently not the 
anterior margin of the dorsal. 
D3,8; A 3, 8 ; C 8, 1, 10, 11, 1, 7 ; V 1, 8 ; P 16. 
The vent is situated close to the anal fin, and nearer the tip of the lower lobe of the caudal 
than the extremity of the snout. The scales, as a general rule, are rather small, thin, and 
sub-circular. The smallest ones occur between the dorsal fin and the occiput, and especially 
upon the latter region. From the middle of the flanks downwards they increase in size, being 
slightly imbricated till near the abdomen, whence they diminish on to the belly, where they 
lose again their imbrication. Radiating grooves affect the posterior section or half of the scale 
only. The lateral line undergoes a gentle downwards curve upon the middle of the abdomen, 
where it is nearer the abdominal than dorsal outline, passing through the area of the largest 
scales, being very conspicuous from head to tail. 
The color is of a uniform yellowish brown tint on the head, and along the dorsal region 
covered with the smallest scales. The sides and belly are shining silvery white. The fins 
being yellowish, the inferior ones lighter than the upper. 
List of specimens. 
Catal. 
No. 
Cor. No. 
of teeth. 
No. of 
spec. 
Locality. 
When 
collected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
245 
2797 
8 
Zuni river. 
1852 
Capt. L. Sitgreaves. 
Alcoholic. 
Dr. S. W. Woodhouse... 
TIGOMA, Girard. 
Gen. Char. —Bears a genera] resemblance to Gila, from which it differs by a much smaller mouth, and larger scales, and the 
scales of the dorsal region, though smaller than on the sides, are not so disproportionate as in the genus just alluded to. The 
ventrals are inserted in advance of the anterior margin of the dorsal, and the Caudal fin is furcated. It is not deemed superfluous 
to state that there are no barbels at the angle of the mouth ; and a characteristic of this genus, as distinct from Gila, consists in 
its terminal mouth and even jaws. The pharyngeal bones resemble very much those of Gila, but the inferior limb is not quite 
so long, the convexity not quite so expanded, and the upper limb more curved inwards. As to the teeth, it requires a minute 
observation to detect a generical difference ; they are more compressed and more strongly hooked ; otherwise, of the raptatorial 
kind, of the hooked type, either without a grinding surface or eise provided with a grinding surface more or less developed. 
They are disposed in the following wise : 2 | 5—5 | 2 ; 2 | 4—5 J 2, or 1 | 4—5 | 2, besides some intermediate formulae. 
Syn.— Tigoma, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 205. 
Some of the species of this genus we had formerly included in other genera, and now we add 
a few more hitherto undescribed. 
