Q6 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY II. 



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. 



Cyprimis (Leuciscus) gracilis, Riciiakdson (1836), Fauna Boreali-Americana, iii, p. 120 

 (Leuciscus gracilis of copyists). 

 Leucosomus gracilis, IIeckel (1H43), Fiscbe Syriens, p. 52 (== Russeger's Reisen, 

 p. 1042). 

 Pogonichthys communis, Girakd ('.856), Proc. Acad. Nat. Sci. Pbila. p. 188, aad else- 

 where. 

 Plaiygohio communis, Gill (1876), Iclitbyology, 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 Platygohio communis, from Milk 

 Eiver, Montana, and elsewhere, with Eichardson's description and figure 

 of Leuciscus gracilis, leaves no doubt of the identity of the two species. 



CATOSTOMID^. 



51. MYXOSTOMA PCEUILURA, S2). nov. 



Torru and general characters of Myxostoma diiquesnii : Body rather 

 elongate, somewhat elevated forward, moderately compressed; the great- 

 est depth 4^ in length ; eye medium, 4i in length ; mouth moderate ; 

 the lips plicate, rather full and subtruncate behind, as in M. aureola, 

 duquesnii, etc. 



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 tin peculiar, strongly forked, the lower lobe in both the types 

 being considerably longer and stronger than the upper lobe. 



Scales 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, diftuse 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 



