50 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. V. 



41. Hybognathus rasconis (Jordan & Snyder). 

 , Notropis rasconis Jordan & Snyder, Bull. U. S. Fish Comm., 1900, 

 121; Rio Verde, near Rascon, San Luis Potosi: Jordan & 

 Evermann, Bull. 47, U. S. Nat. Mus., 1900, 3141. 

 Basin of the Rio Panuco. (Forlon; Valles; Rascon; Rio Verde, 

 Dr. W. L. Tower.) 



FIG. 10. HYBOGNATHUS RASCONIS (Jordan & Snyder). 

 No. 61:3 (Notropis rasconis Jordan & Snyder), Leland Stanford Jr. University. 



Head 4; depth 4; D. 8; A. 8; scales 736 to 42-5. Body rather 

 elongate, aspect of Nototropis heterodon; head small, convex above, 

 interorbital width 2> to 3 ; eye 2% to 3 ; snout $%; teeth 4-4; mouth 

 moderate, the maxillary nearly reaching vertical from anterior margin 

 of orbit; mouth oblique, more so than in preceding species; origin 

 of dorsal fin midway between base of caudal and tip of snout ; longest 

 dorsal ray i> in head; base of dorsal a| in head; pectorals i% in 

 head; ventrals iX m head; lateral line decurved, occasionally missing 

 on a few scales. 



Color dark olivaceous above, lighter below; sides with a well- 

 defined' lateral band ending in a black caudal spot. Length about 

 2^ inches. 



18. Pimelocephales Rafinesque. 

 FLAT-HEAD MINNOWS. 



Pimephales Rafinesque, Ichth. Ohiensis, 52, 1820. (Pimephales 

 promelas Rafinesque). 



Body rather robust, little compressed; head short and rounded; 

 mouth small, inferior; upper jaw. protractile; no barbels; teeth 4-4, 

 with oblique grinding surface, usually but one of the teeth hooked; 

 dorsal fin opposite ventrals, its first (rudimentary) ray separated 

 from the rest by a membrane, and not adnate to the first developed 

 ray, as is usual in minnows (most distinct in adult males, in which 

 the skin of the first ray is thickened); anal base short; alimentary 

 canal elongate, about 2% times the length of the body; peritoneum 

 black; lateral line complete or missing on some scales. A small group 

 of minnows inhabiting streams east of the Rocky Mountains and 

 south to Chihuahua. 



