788 BULLETIN UNITED STATES GEOJiOGICAL SURVEY. 



D. Teeth subconic, little hooked, wide set. 



Ptychochilus. 

 DD. Teeth compressed, hooked, close set. 

 — Caudal peduncle very slender, the basal caudal rays 



much developed Gila. 



Caudal peduncle stout, the basal caudal rays little 



developed Telestes.* 



CC. Teeth raptatorial, with developed grinding surface. 



E. Teeth 2, 5-4 or 5, 2 or 1 Squalius. t 



EE. Teeth 4-5 or 5-5 LEUCOS.t 



kk. Maxillary with a small barbel ; teeth hooked. 

 F. Premaxillaries projectile, a groove separating the upper lip 

 from the forehead. 

 G. Teeth 2, 4-5-2, without grinding surface ; barbel minute, 

 not at the end of the maxillary ; dorsal more or 



less posterior to ventrals Semotilus, 



GG. Teeth 2, 5-4, 2, or 2, 5-5, 2, with grinding surface; barbel 

 terminal. 

 — Caudal fin symmetrical, the rudimental basal rays little 



developed Svmmetrurus.§ 



Caudal fin unsymmetrical, the rudimental basal rays 



largely developed Pogonichthys. 



GGG. Teeth in the principal row 4-4; barbel terminal. 



I. Teeth without grinding surface. 



J. Dorsal behind ventrals ; scales small ; teeth mostly 1, 



4-4, 1 Apocope. 



JJ. Dorsal over ventrals or slightly posterior ; scales moder- 

 ate or rather large. 



K. Teeth 4-4, or 1, 4-4, 1 Ceratichthys. 



KK. Teeth 2, 4-4,2 Couesius. 



II. Teeth with developed grinding surface. 



L. Dorsal fin more or less directly above ventrals ; scales 



large ; teeth 2, 4-4, 2. 

 LL. Dorsal fin wholly behind ventrals ; scales small ; teeth 



4-4 Agosia. 



FF. Premaxillaries not projectile ; teeth mostly 2, 4-4, 2, with- 

 out grinding surface ; scalessmall; dorsal behind 



ventrals; barbel terminal Rhinichthys. 



jj. Teeth molar, of the grinding type, two or three of the main row 

 blunt and much enlarged; teeth in three rows, 

 the outer deciduous, 2 or 3, 2, 5-4, 2, 2 or 3. 

 M. Upper jaw not protractile; no barbel; dorsal fin beginning behind 



' ventrals Mylopharodon. 



MM. Upper jaw protractile ; maxillary with a barbel ; dorsal over 



ventrals Mylochilus. 



tt. Pharyngeal teeth quite rudimental, replaced by a somewhat uneven ridge of the 



bone. (^Graodontince.) 

 N. Dorsal fin short, without spinous ray, opposite ventrals; anal 

 basis short ; mouth small, without barbel, the 

 upj)er jaw somewhat the larger ; intestinal canal 

 short; lateral line complete Graodus. 



* Telestes Bonaparte = Tigonia, Siboma, and Clinostomus Grd. 



t Squalius Bonaparte = Cheonda Grd. 



t Leucos Heck el = Myloleucus Cope. 



§ Symmetrurus, gen. nov. ; type PogonicMliys argyreiosus B. & G. 



