362 



SYNOPSIS OF THE CYPPJNIDiE OF PENNSYLVANIA. 



SEMOTILUS, Rafinesque. 

 Leucosomus, Heckel and Girard. 



This genus, with Ceratichthys, represents the European Gohio ; fifteen species of the 

 two former, with two of Platygobio, Gill, take the place in North America of the two 

 known of the latter. The above synonyme was the result of an overlooking of the bar- 

 bels, which are sometimes quite obscure. None of the species have the muzzle depressed 

 or the mouth inferior as in the previous genus; this with the head, is obtuse and massive; 

 the general form is deeper. The scales are large and present strong radii. Length of in- 

 testinal canal nearly equal that of head and body. 



Lateral line originating below upper angle of operculum ; scales large 45-7 in lateral line. RHOTHETJS. 



Lateral line origin at superior angle of operculum; scales smaller; I. 1. 57-9 ; black spot at base of dorsal fin ; 

 eye 5 to 5 J times in head. corporalis. 



Lateral line origin at superior margin operculum, scales smallest 9— G3-5— 7 ; elongate, muzzle long, eye one- 

 sixth head; dark spot at base dorsal, no dark on sides, head, or body. pallidus. 



SEMOTILUS RHOTHEUS, Cope. 



Proc. Acad. Phila., 1861, 564, S. corporal-is, Abbott, do. 1861, 154 

 (not Ci/prinus corporalis, Mitchell). Squalius hyalope, Cope, ibid. 

 1864, 280. 



This species and the next have a very broad prcorbital bone, and 

 the eye nearer the end of the muzzle than the opercular border. The 

 posterior end of the margin of the operculum is above opposite the inferior margin of the 

 orbit in both. 



The S. rhothcus is the largest of our Cyprinidsc, reaching a length of eighteen inches. The dorsal line is 

 arched and is continuous with the rather steep slope of the cranium to the labial border. Scales 8—45-7—5, a 

 nearly equal portion exposed on the anterior and posterior parts of the body. The dermal sacs which hold them 

 are black-margined, and extend beyond the tip of the preceding scale. Fins D I. 8. P. 17. V. 8 A. 8 (J. 18. 

 The head is broad, frontal width equalling one-half of superior length, muzzle rather short; the eye enters Dearly 

 twice into length of latter, and five times into that of the head. The head is one-fourth the length to the base of 

 the caudal. 



The colors of this species are particularly brilliant, having as ground a very pure silver 

 white. The dorsal region is often steel-blue and the preopercular and subocular regions 



