1915.] NATURAL SCIENCES OF PHILADELPHIA. 211 



Puerto, on or near the lower course of the Huallagua River, Peru. 

 1873. James Orton. Presented by E. D. Cope. 



This species seems representative of Rhamdia quelen (Quoy and 

 Gaimard) from eastern Brazil and the La Plata, and agrees largely 

 in its long adipose fin. From R. humilis (Giinther) from Venezuela,- 

 with which it was formerly identified, it differs in the longer adipose 

 fin. It also differs from R. cinerascens (Giinther) from western 

 Ecuador and R. pentlandi (Valenciennes) from the Peruvian Andes 

 in similar fashion. 



Rhamdia mounseyi Regan,^ from the Ucayali River, has the occipital 

 process extending f to the dorsal, origin, the gill-rakers 2 or 3 + 5 

 on lower part of arch, and the maxillary barbels extending beyond 

 the anal fin. 



(Named for Rioja, the type locality.) 



Rhamdia ortoni sp. nov. Fig. 3. 



Head 3 A; depth 6*; D. I, 6; A. iv, 8; P. I, 8?; V. i, 6; head 

 width If in its length; head depth at occiput 2; snout 2f ; eye 5i; 

 maxillary 4|; interorbital 2|; dorsal spine 2j; third dorsal ray 

 If; least depth of caudal peduncle 2f ; ventral 1|. 



Body compressed, elongate, slender, deepest at dorsal origin, 

 and edges all convex. ■ Caudal peduncle well compressed, least 

 depth about f its length. 



Head depressed, moderately broad, convex above and below, 

 profiles similar. Snout wide, broadly convex over surface, length 

 f its greatest width. Eye ellipsoid, close to upper profile and 

 hind edge near middle in length of head. Eyelids free, not 

 adipose-like. Mouth broad, transverse, and lower jaw very slightly 

 protrudes. Teeth fine, villiform, in rather narrow bands in jaws, 

 which contiguous. No vomerine or palatine teeth. Tongue wide, 

 thick, fleshy, depressed, not free. ^Maxillary barbel extends to 

 ventral origin. Outer mental barbel extends nearly far back as 

 tip of depressed pectoral, inner mental barbel to pectoral origin. 

 Posterior internasal area slightly greater than anterior, and all 

 nostrils simple pores. Interorbital broadly convex. Fontanel large, 

 extends back opposite hind pupil edges. Occipital process extends 

 I to dorsal origin. Humeral process rather short. Opercle broadly 

 triangular, with numerous radiating striae. 



Gill-opening extends forward about first fourth in head. Rakers 

 2-1-7, firm, lanceolate, several of larger with several denticles, about 



3 Ann. Mag. Nat. Hist., London, (8), XIII, 1913, p. 281. 



