PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 83 



teetli are 2, 4-5, 2, not 2, 5-5, 2, ami the folding of the lips, which sug- 

 gested the name Ptychochihts, is not an evident feature to me. 



This species, which is the type of the geuus Ptychochilus, is a true 

 species of the genus Gila as the characters of that genus are now under- 

 stood. The general physiognomy is similar, the head is long, slender, 

 and depressed, the mouth is very large and overlapped by the snout, 

 the caudal peduncle is slender ; the scales are similarly small and 

 loosely imbricated, the dorsal fin is slightly behind the ventrals, the 

 aual fin is not elongate ; the lips are normal ; the pharyngeal teeth are 

 two rowed, the inner row 5-4 or 5-5, and the intestinal canal is short. 

 In all these respects, the type of Ptychochiliis agrees with the type of 

 Gila, and as no generic difference has been ahov! u, Ptychochilus becomes 

 a synonym of Gila. At present, the fishes called Clinostomus by Girard 

 are referred to Gila. The two groups ought to be generically distin- 

 guishable. The typical species of each are very different in physiog- 

 nomy, but at present, as has been shown by Prolessor Cope, we are 

 unable to draw a line between them. 



The other species referred to Ptychochiliis are probably distinct from 

 oregonensis, but should be comj)ared with species of Gila and with each 

 other. If rapax and lucius have really the teeth 2, 4-4, 2, it may be 

 necessary to frame a separate genus for them, as they would hardly be 

 referable to Notropis or to Gila. 



7- ACROCHILUS ALUTACEUS Agassiz 6t Pickering. 



Hard-Mouths. 



1855 — Acrocheilus alutacem Agas.siz & Pickering, Amer. Jouro. Sci. Arts, xix,p.96. 

 Luvinia alittacea Girard, Proc. Ac. Nat. Sc. Phila. 1856, p. 184. 

 Acrochilus alutacem GxJnther, Cat. Fishes Brit. Mus. vii, p. 276, 1868. 

 Aerochilus alutaceus Jordan & Copeland, Check List Fishes, p. 146, 1876. 



Acrochilus alutaceus Jordan, Catalogue Fishes N. A. p. 418, 1878. 



Several fine specimens of this very interesting species are in Mr. 

 Stone's collection. As no detailed account has been given of the fish, 

 and as none of the authors mentioned in the above synonymy, excepting 

 Prolessor Agassiz, seem ever to have seen it, I give a description of one 

 of the specimens. The relations of this genus are doubtless with 

 Chondrostoma, but its teeth are fewer and differently formed. 



General form and appearance of the species of Gila, but the head not 

 depressed, and more blunt forward. 



Body elongate, not much compressed, its sides more so than the cau- 

 dal peduncle ; the greatest depth, over the ventrals, 4 in length; caudal, 

 peduncle very long and very slender, unusually broad, nearly terete, its 

 length contained 4§ times in the length of the body, its least depth 2§ 

 in length. 



Head moderate, 4^ in length of body, bluntish, the profile considera- 

 bly rounded, the interorbital space strongly convex. Mouth horizontal, 



