1911.] NATURAL SCIENCES OF PHILADELPHIA. 497 



caudal lobes very indistinctly mottled with pale gray spots, or 

 leaving incomplete short wavy lines of darker color somewhat trans- 

 versely over these portions of fin-rays. Adipose fin pale or dull 

 olive-brown. Pectoral and ventral pale brownish to whitish, former 

 with median upper portion a little grayish or darker. Anal pale 

 basally, though greater outer or distal portion quite dusky. 



Length 5J inches. 



Type, No. 1. Collection, S. N. Rhoads. Affluent of the Chimbo 

 River near Bucay, Province of Guayas, Ecuador. July, 1911. 



Only a single example of this species, described above, was obtained. 

 It differs from Prochilodus humeralis Giinther 1 chiefly in coloration, 

 that species being marked with a black shoulder spot on the fourth to 

 sixth scales of the lateral line and the dorsal with blackish dots pos- 

 teriorly, though the other fins and base of the caudal are immaculate. 



Other species from the eastern drainage of South America which 

 I have examined are, of course, entirely different in coloration, viz.: 

 P. steindachneri Fowler, P. ortonianus Cope, P. cephalotes Cope, 

 P. teraponura Fowler and P. amazonensis Fowler. 



{Zriyfia^ blotch; oupa } tail; with reference to the dark caudal 

 blotch.) 



RHOADSIN.E. 



Preventral region rounded, without keel. Dentition perfected. 

 Jaws peculiar, well back, and long mandible articulated below hind 

 edge of eye. Dorsal and anal rays elongated. Adipose fin present. 



I have framed this subfamily for the single aberrent genus described 

 below. It is remarkable for the constriction of the jaws, somewhat 

 suggestive of the salmonoid Plecoglossus. Its affinities are likely 

 near the Tetragonopterince. 



EHOADSIA gen. nov. 



Type Rhoadsia altipinna sp. nov. 



Body deep, compressed. Belly rounded. Mouth cleft large, 

 deep. Front jaw teeth in adult largely uniserial, strong, compressed, 

 each with large pointed median denticle and two graduated smaller 

 denticles each side, of which outer or lower smaller. Sometimes 

 three or four external short conic teeth on upper lip in adult, absent 

 in young. In young anterior jaw teeth all broader, with more 

 uniform cutting-edge, as denticles all more on a line and median 

 denticle but slightly enlarged. Adult with a single series of conic 



1 Proc. Z. S. London, 1859, p. 419. Western Andes of Ecuador. 



