148 OSTARIOPHYSI. 
Pantosteus plebeius, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 170*; Meek, Publ. 
Columbian Mus., Zool. v. 1904, p. 80°. 
Catostomus conchos, Meek, t. c. p. 83, t. 7°. 
Depth of body 4 to 5 in the length, length of head 44 to 42. Diameter of eye 5 to 6 in the length of head, 
length of snout 23, interorbital width 21 to 24. Snout obtuse. Lips papillose; lower lip deeply 
incised ; width of mouth 2 the width of head. 80 to 95 scales in a longitudinal series. Dorsal 10-11, 
the 2 anterior rays simple; origin nearly equidistant from tip of snout and base of caudal; free edge 
straight ; longest ray longer than the base of the fin. Anal 8, the 2 anterior rays simple, the fin, when 
laid back, extending to the base of caudal. Pectoral shorter than the head, extending 3 to ? of the 
distance from its base to the origin of ventral, which is nearly below the middle of the dorsal. Caudal 
emarginate. Brownish, mottled with darker. 
Hab. Mexico, Chihuahua and Durango: 
Rio Casas Grandes!?5, Rio Santa Maria®, Rio Carmen®, Rio Sauz® and 
Rio Conchos °° in Chihuahua; Rio Nazas® and Rio Mezquital° in Durango. 
Here described from seven specimens, the largest 150 mm. in total length, from the 
R. Casas Grandes and the R. Nazas (eek). The species attains a length of 450 mm. 
From Girard’s figure I should have thought that C. guzmaniensis was a distinct 
species, differing in having a longer dorsal fin with 13 rays and in coloration, the back 
and sides being dark, with an orange lateral band. I place it in the synonymy on the 
authority of Dr. Meek, who states that this is the coloration of adult males. 
2. Catostomus bernardini. 
Catostomus bernardini, Girard, Rep. U.S. & Mex. Bound. Surv., Fish. p. 40, t. 23. figs. 1-5 
(1859); Jord & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 178°; Meek, Publ. 
Columbian Mus., Zool. v. 1904, p. 32°. 
Catostomus sonorensis, Meek, |. c. *. 
Differs from the preceding especially in the larger scales, 65 to 75 in a longitudinal series, 
Hab. Mexico, Sonora! 2 3 4, 
4, XYRAUCHEN, Eigenm. & Kirsch, 1888. 
Xyrauchen, Jord. & Everm, Bull. U.S. Nat. Mus. xlvii. 1896, p. 184. 
This genus differs from Catostomws in having a sharp-edged hump behind the 
occiput, produced by the remarkable development of the expanded plate-like anterior 
interneural bones. It comprises two species from the Colorado River System, one of 
which has been recorded from Horseshoe Bend, on the border of Sonora. 
1. Xyrauchen cypho, Lockington, 1880. 
Xyrauchen cypho, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 184°; Meek, Publ. 
Columbian Mus., Zool. v. 1904, p. 33%. 
Hab. Cotorapo River ! 2, 
