66 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY—IL. 
americanus. Prof. Cope states that it is “ probably a Lavinia”, but he 
has not yet given ns the grounds for his opinion. The figure of Cuvier 
and Valenciennes certainly bears little resemblance to Lavinia. 
50. PLATYGOBIO GRACILIS, (Richardson) Gill & Jordan. 
Cyprinus (Leuciscus) gracitis, RICHARDSON (1836), Fauna Boreali-Americana, iii, p. 120 
(Leuciscus gracilis of copyists). 
Leucosomus gracilis, WeCKEL (1843), Fische Syriens, p. 52 (= Russeger’s Reisen, 
p. 1042). 
Pogonichthys communis, GIRARD (:856), Proc. Acad. Nat. Sci. Phila. p. 188, and else- — 
‘where. 
Platygobio communis, GILL (1876), Ichthyology, Capt. Simpson’s Expl. p. 408, and 
and in previous papers. 
Leucosomus communis, GUNTHER (1867), Cat. Fishes Brit. Mus. vii, p. —. 
Comparison of various specimens of Platygobio communis, from Milk 
River, Montana, and elsewhere, with Richardson’s description and figure 
of Leuciscus gracilis, leaves no doubt of the identity of the two species. _ 
CATOSTOMID. 
51. MYXOSTOMA PQCSCILURA, sp. nov. 
Form and general characters of Myxostoma duquesnii: Body rather 
elongate, somewhat elevated forward, moderately compressed; the great- 
est depth 44 in length; eye medium, 44 in length; mouth moderate; 
the lips plicate, rather full and subtruncate behind, as in WM. aureola, 
duquesnii, ete. . 
Dorsal fin medium, of 13 developed rays; anal high, reaching when 
depressed considerably beyond base of caudal in one specimen, falling 
short in the other; pectoral fins rather long ; ventrals with ten rays. 
Caudal fin peculiar, strongly forked, the lower lobe in both the types 
being considerably longer and stronger than the upper lobe. 
Seales large, 5-43-4. 
Coloration of the body usual; of the fins quite unlike any other mem. 
ber of the genus. | 
Dorsal fin (in the type-specimens preserved in alcohol) chiefly red, 
with traces of a blackish bar about half-way up; pectorals chiefly red, 
whitish in front, with a large, elongate, diffuse black blotch near the 
middle ;’ ventrals reddish, blackish toward their base ; anal faintly red- 
dish ; the membrane black. . 
Upper lobe of the caudal fin red ; lower lobe chiefly jet-black, except 
the last two developed rays and their membranes, which are abruptly 
