148 OSTARIOPHTSI. 



Pantosteus pleheius, Jord. & Everm. Bull. U.S. Nat. :i\rus. xlvii. 1896, p. 1~0'; Meek, Publ. 



Columbian Mus., Zool. v. 1901<, p. 30'. 

 C'atostomus conchos, Meek, t. c. p. 33, t. 7 °. 



Depth of hod}- 4 to 5 in the length, length of head 4;| to 43. Diameter of eye 5 to G in the length of head, 

 length of snout 2|, iaterorbital width 21 to 2.1. Snout obtuse. Lips papillose ; lower lip deeply 

 incised; width of mouth l tlie width of head. SO 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 tin. Anal 8, the 2 anterior rays simple, the fin, when 

 laid back, extending to the base of caudal. P(^ctoral shorter than the head, extending .^ 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. 



Hah. Mexico, Chihuahua and Durango : 



Hio Casas Grandes ^ " ^, Eio Santa Maria'"', Rio Carmen''', Rio Sauz ^ and 

 Rio Conchos -^ *' in Chihuahua ; Rio Nazas ^ and Rio Mezquital ' in Durango. 



Here described from seven specimens, the hirgest 150 mm. in total length, from the 

 R. Casas Grandes and the R. Nazas {Meek). The species attains a length of 450 mm. 



From Girard's figure I should have thought that C. giizmaniensis 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 baud. 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, Pubk 

 Columbian Mus., Zool. v. 1904, p. 32'. 



Catostomus sonorensis, Meek, 1. c. '. 



Difl'ers from the preceding especially in the larger scales, G5 to 73 in a longitudinal series. 



Ilah. Mexico, Sonora i 2 3 4_ 



4. XYRAUCHEN, Eigenm. & Kirsch, 1S8S. 

 Xyrauchen, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 189G, p. 184.. 



This genus differs from Catostomus 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. 181'; Meek, Pabl. 

 Columbian Mus., Zool. v. 1904, p. 33 '. 



Ilah. Colorado River i ". 



