226 Bulletin 47, United States National Museum. 



115. GILA,* Baird & Girard. 

 Gila, BAIRD & GIRARD, Proc. Ac. Nat. Sci. Phila., 1853, 368, (robusta). 



Body elongate, little compressed, the back arched, especially in the 

 adult ; the caudal peduncle typically extremely long, slender, contracted, 

 much narrower than the base of the caudal fin, which is widely forked, 

 with its basal fulcra very much developed. Head in typical species 

 broad, depressed, its profile concave. Mouth large, horizontal, and over- 

 lapped by the broad snout. Dorsal fin behind the middle of the body, 

 slightly behind ventrals. Anal basis short. Intestinal canal short. 

 Scales very small, little imbricated, sometimes scarcely imbricate at all, 

 longer than deep, especially posteriorly. No barbel. Pseudobranchise 

 present. Teeth 2, 5-4, 2, close set, compressed and hooked, without 

 grinding surface. Vertebrae 42 to 46. Peritoneum dusky. Species of 

 large size, the typical form remarkably unlike the usual Cyprinoid type, 

 but varying through a series of intermediate forms directly into Leuciscus, 

 so that the genus has no very satisfactory technical character. (Gila, the 

 name of the river where the typical species was first obtained.) 



a. Belly more or less fully scaled. 



b. Caudal peduncle very slender, its least depth 1% in maxillary ; scales of back and belly 



much reduced. ELEGANS, 360. 



bb. Caudal peduncle not very slender, its least depth 1% * n maxillary ; scales of back and 



belly moderately reduced. ROBUSTA, 361. 



aa. Belly naked ; caudal peduncle slender ; anterior profile scarcely concave. 



6EMINUDA, 362. 



360. GILA ELEGANS, Baird & Girard. 

 (BoNT-TAii.; "GILA TROUT.") 



Head 5 ; depth 5 ; eye 5. D. 9 j A. 10 ; scales 23-85-10 ; teeth 2, 4-5, 2. 

 The extreme species of this type. Body elongate, somewhat compressed, 

 the region before the dorsal elevated, forming a sort of hump, the dorsal 

 fin inserted on the downward slope of the back, so that its base is quite 

 oblique. Caudal peduncle extremely long and slender, as broad as deep, 

 and nearly terete, its length (from end of anal to middle of base of 

 caudal) li times the length of the head, its least depth If in maxillary; 

 its extremity dilated and compressed. Head short, broad, the snout 

 depressed and broadly rounded; the anterior part of the head from 

 behind the eyes broad and depressed ; the posterior part high so that the 

 profile forms a concave arc. All these traits of form more marked in old 

 examples ; young specimens (emorii) having the anterior profile scarcely 

 concave. Mouth rather larger than in G. robusta, nearly horizontal, the 

 upper lip on the level of the lower part of orbit, the maxillary extend- 

 ing to the front of orbit, the lower jaw on all sides included ; skin 



*"The food of Gila elegaw consists almost entirely of Gasteropoda and caddis worms, which 

 they crush with their powerful pharyngeals. The young differ greatly from the old, the cra- 

 nium probably not becoming depressed until the second year. They are very tenacious of life. 

 They have revived after being several hours out of the water and having become perfectly dry 

 and stiff. They take the hook freely." (W. L. Carpenter, in Kirsch, Proc. U. S. Nat. Mus., 

 1888, 558.) 



