MAY, 1902. THE ICHTHYOLOGY OF MEXICO MEEK. 75 



of anterior rays to base of posterior. Tip of dorsal fin rounded; 

 scales 7-38 to 41-6. 



Color light brownish, silvery below; the middle of each scale 

 silvery, forming indistinct silvery lines along the rows of scales. 

 Longest specimen 10% inches in length. Santa Rosalia; Jimenez. 



Pantosteus plebius (Baird & Girard). 



This species is very variable. The dorsal fin usually has 9 

 rays, occasionally 10, seldom u. Scales in the lateral line 

 range from 85 to 100. 



A study of a large series from Colonia Juarez, Mifiaca and 

 San Andres indicates that but one species of Pantosteus exists in 

 this region. Colonia Juarez; Ahumada; San Andres; Mifiaca. 



Catostomus sonorensis, sp. nov. 



Type, No. 3564, F. C. M. Length, 5| inches. 



Locality, Rio Paphigochic, Mifiaca, Chihuahua, Mexico. 



Head 4; depth 4?^; D. xii; A. 7; scales 11-65-10. Body 

 robust; profile very convex; top of head flattish, broad, 

 interorbital 2^ in head; snout blunt, 2^ in head; eye large, 4^ 

 in head; lips thick, papillose; papillae in eight or nine rows on 

 upper lip. The two halves of upper lip meet at a very obtuse 

 angle. Dorsal fin as high as long, its base i|^ in length of head, 

 its margin slightly concave. The tips of first rays reaching 

 middle of last ray when the fin is deflexed; tips of last dorsal 

 rays opposite tips of ventrals, which r,each to vent; pectoral i^ 

 in head; ventrals ij. 



Origin of dorsal fin slightly nearer base of caudal than tip of 

 snout; caudal deeply emarginate, lobes equal; scales small on 

 anterior half of body. 



Color steel blue to brownish, white below. Young specimens 

 have the dark lateral blotches. 



This species differs from Catostomus bernardini in having 

 larger scales. Mifiaca. 



Catostomus corichos, sp. nov. 



Type, No. 3557, F. C. M. Length, 10.64 inches. 



Locality, Rio Conchos, Jimenez, Chihuahua, Mexico. 



Head 4^; depth 4^; D. xi; A. 7; scales 13-80-13. Body 

 robust, terete, not much compressed, except posterior third; 

 snout blunt, its length 2? { in head; lips thick, papillose, about 



