Family IV. Catostomid>e. 31 



Streams and lakes on the plateau in northern Mexico, ranging as far 

 south as the headwaters of the Rio Mezquital in Durango, and the 

 Rio Nazas. (Sauz; Lerdo; Santiago Papasquiaro; Durango.) 



Head \% to 4^; depth \]/ 2 \ D. 9 to 11; A. 8; scales 14-85 to 100- 

 14. Body elongate, rather stout, little compressed; upper surface of 

 head convex, mouth inferior; lips papillose, papillae on upper lip in 

 about six rows; free margin of lower lip incised, the incision reaching 

 about half-way to margin of jaw; interorbital convex, its width 21 in 

 head; eye small, high up on the head, its diameter about from 5-6^2 

 in head; snout 2 J in head; origin of dorsal nearer tip of snout than 

 base of caudal; dorsal low, its margin convex, its longest ray about i| 

 in head; base of dorsal i\ in head; pectorals moderate, \]/$ in head, 

 and slightly more than the space between their tips and base of caudal ; 

 ventral fins i-g in head, their tips reaching half-way to base of anal; 

 caudal peduncle somewhat compressed, its least diameter 2I in head; 

 caudal fin very short, emarginate, its longest rays \% in head; scales 

 small, those on anterior half of body smaller than those on posterior 

 half, or on ventral surface; about 50 scales in a series between nape 

 and dorsal fin. 



Color dark brown, the sides mottled with darker; in small speci- 

 mens a dark lateral band; in large males in life, the side has a bright 

 orange band. Length 12 to 18 inches. 



This species is easily recognized on account of the small scales, 

 hard cartilaginous lips, and short fins, and especially by the short 

 caudal fin. It is usually very abundant where found, and seldom ex- 

 ceeds 12 inches in length. 



11. Ca tost 011ms Le Sueur. 



Fine-scaled Suckers. 



Catostomus Le Sueur, Jour. Acad. Nat. Sci. Phila., 1817, 89. (Type, 

 Cyprinus catostomus Forster.) 



Body elongate, terete anteriorly, not much compressed; mouth 

 rather large, inferior; upper lip thick, papillose; lower lip greatly 

 developed, with broad, deeply incised free portion; scales small, those 

 on anterior half of the body much reduced in size; pharyngeal teeth 

 compressed vertically, rapidly diminishing in size upward; lateral line 

 nearly straight, well developed; air bladder in two parts; vertebrae 45 

 to 47. Species chiefly North American. 



KEY TO THE SPECIES OF CATOSTOMUS. 

 a. Scales large, 60 to 75 in the lateral series; not 

 more than 35 in a series between nape and 

 dorsal fin. 



