1856.] 205 



About three years since, the genus 



Gila, B. & G. 

 was proposed, to include species whose body was subfusiform, compressed, with 

 the back more or less arched, especially in large and old specimens, and some- 

 times tapering very much posteriorly, with the peduncle of the tail very slender. 

 The head being depressed and proportionally small, with its upper outline often 

 concave ; the snout is elongated ; the eyes are of moderate size ; the isthmus 

 small. The mouth is of medium size, the upper jaw overlapping the lower, so 

 as to conceal its cleft from above. No barbels, or rudiments of barbels. The 

 pharyngeal bones are well developed, the inferior limb, elongated, the upper one 

 forming an open curve ; the'convexity being somewhat expanded, the expansion 

 tapering along the upper and inward limb. The teeth are well developed, of 

 the raptatorial kind of the hooked type, without grinding^surface, subcylindrical 

 slightly compressed and disposed upon a double row of one or two and four or 

 five as follows : 1 | 4 5 | 2, or even, 2 | 4 5 | 2. The ventral fins are inserted 

 in advance of the anterior margin of the dorsal. The caudal is bifurcated. 

 The scales are small on the dorsal region and of medium size on the sides, and 

 longer than high. The lateral line forms an open curve along the middle of 

 the abdomen. 



The species which we now include in this genus, are the following : 



1. Gila robusta, B. & G. Proc. Acad. Nat. Sc. Phila, vi. 1853, 368; and in 

 Siiffr. Rep. Zuni and Color. Riv., 1853, 148. Fishes, PI. I. 



From Zuni River. Dr. Woodhouse. 



2. Gila elegans, B. & G. Proc. Acad. Nat. Sc. Phila. vi. 1853, 3G9; and in 

 Sitgr. Rep. Zuni and Color. Riv. , 1853, 149. Fishes, PL II. 



Specimens from Zuni River, collected by Dr. Woodhouse ; from the Colorado, 

 collected by A. Schott, under Major Emory, and from the Gila, collected by 

 Dr. Heermann, under Lieut. J. G. Parke, U. S. A. 



3. Gila gracilis, B. & G. Proc Acad. Nat. Sc. Phila. vi. 1853, 369; and in 

 Silgr. Rep. Zuni and Color. Riv., 1853, 151. Fishes, PI. III. 



From Zuni River. Dr. Woodhouse. 



4. Gila grahamii, B. & G. Proc. Acad. Nat. Sc. Phila. vi 1853, 389. 

 From Rio San Pedro, a tributary of the Rio Gila John H. Clark. 



5. Gila emorii, B. & G. Proc. Acad. Nat. Sc. Phila. vi. 1853, 388. 

 From Gila River, collected by Dr. John L. Leconte. 



"We separate from the genus Gila, under the name of 



TIGOMA, 

 some species formerly excluded by us in other genera, to which we add a fev/ 

 others not hitherto described. They all bear a general resemblance to Gila, 

 from which they differ by a much smaller mouth, and larger scales, and those 

 of the dorsal region, though smaller than on the sides, are not so disjjropor- 

 tionate. The ventrals are inserted in advance of the anterior margin of the 

 dorsal, and the caudal is bifurcated. It is not deemed superfluous to state that 

 there are no barbels at the angle of the mouth, and a characteristic of this o-e- 

 nus as distinct from Gila, consists in its tei'minal 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 

 difference ; they are more compressed and more strongly hooked, otherwise of 

 the raptatorial kind, of the hooked type either without a grinding surface, or 

 else a grinding surface more or less developed. They are disposed in the fol- 

 lowing wise : 2 | 5 5 | 2, 2 | 45 | 2, or 1 ] 45 | 2, and some intermediate 

 formulas. 



A. Teeth without grinding surface. 



