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. bi 53 [Notropis rasconis Jordan & Snyder), Leland Stanford Jr. University. 



Head 4; depth 4; D. 8; A. 8; scales 7-36 to 42-5. Body rather 

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

 interorbital width 2 y 2 to 3 ; eye 2 2 / z to 3 ; snout 3 yi ', 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}4 in head; base of dorsal 2 J in head; pectorals i* in 

 head; ventrals x% in 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. 



1<S. Pimelocephales Rafmesque. 

 Flat-head Minnows. 



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

 promelas Rafmesque). 



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. 



