154 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY — IV. 



minutely tuberculate and the fins are bright yellow. Head 4; depth 4. 

 D. 7; A. 8; scales 16-85-10; teeth usually 5-5. L. 2-3 inches. Penn- 

 sylvania to Dakota and Tennessee; abundant in small streams; one of 

 the most beautiful of our fishes. 



(Luxilus or Chrosomus enjthrogaster Raf. Ichth. Oli. 1820, 47: Luxihis erythrogaster 

 Kii-t. Boat. Joum. Nat. Hist, iv, 23, fig. 1844 ; Cope, Cypr. Penu. 391 : Lmciscus ery- 

 throyasier Giiuther, vii, 247 ; Jordan, 302.) 



** Sides of body with the upper band beginning opposite the vent and extending 

 backward to the middle of the caudal, terminating iu a black spot; lower 

 band extending from snout through eye, downward and backward, ceasing 

 at base of anal ; back with dark spots and cross-bars. 



1'3'§. C. oreas Cope. 



Form of the preceding, the snout rather more obtuse. Coloration 

 similar to that of the preceding, except for the diflerence in pattern. 

 The back clear olive-green, with dark cross-bars ; belly, interspace be- 

 tween the lateral bands, and bases of vertical fins bright crimson; fins 

 otherwise yellow. Head 4; depth 4 J. D. 8; A. 8; Lat. 1. 67; teeth 

 5-5. L. 2i inches. Tennessee and Eoanoke Elvers; even more brill- 

 iant than the i^receding. 



(Cope, Journ. Acad. Nat. Sci. Phila. 18(38,233.) 

 *** Body with two black lateral bands on the side, which unite on the caudal x)edun- 

 cle, the lower broader, decurved, the upper narrow and straight. 



179, C cos Cope. 



Slenderer than the preceding ; the lateral line less distinct, often en- 

 tirely wanting. Variations in color as in the other species. Head 4; 

 depth 5. D. 8; A. 8; Lat. 1. 77; teeth 5-5. L. 2 J inches. Susquehanna 

 Eiver. Perhaps a variety of G. erytlirogaster. 



(Cope, Proc. Acad. Nat. Sci. Phila. 1801, 523; Cope, Cypr. Penn. 391.) 



76.— aOPiaE'^DUM Jordan. 



(Jordan, Bull. Hayden's Geol. Surv. Terr, iv, 786, 1878: type Hyhorhynclius sidcriits 

 Cope.) 

 This genus is very closely related to Ri/hognathns, differing only in 

 the small size of the scales, there being 55-90 in the course of the 

 lateral line. The jihysiognomy is somewhat different, and the dorsal 

 fin is inserted more posteriorly than usual in EyhognatJms. As in Ryho- 

 (jnathiiSj the teeth are 4-4, scarcely hooked, with narrow grinding surftice, 

 and the intestinal canal is elongate, the peritoneum black. Eocky 

 Mountain region; one species in Western Mexico.* {Zo(p(K, darkness; 

 evfJov, within ; in allusion to the black peritoneum.) 

 * Scales very small, 85-90 in the course of the lateral line. 



*Z. australe Jordan. Body rather elongate, formed much as in Campostoma aiioma- 

 lurn, somewhat compressed, the back somewhat elevated and rounded anteriorl5''. 

 Head rather large, slightly dejiressed above. Mouth moderate, low; the lower jaw 



