1914.] 



NATURAL SCIENCES OF PHILADELPHIA. 



259 



Head depressed, profiles similar, well convex bulging sides slightly 

 constricted above, and under surface broadly convex. Snout 

 broadly depressed or very slightly convex, its length about f its 

 width opposite front eye edges. Eye ellipsoid, superior, impinging 

 on upper profile, and centre midway in head. Eyelids free, not 

 adipose-like. Mouth moderate, transverse, commissure very short. 

 Broad bands of villiform teeth in jaws, lower f width of upper and 

 latter with posteriorly directed angle at each end. No other teeth 

 in mouth. Inner buccal folds moderately broad. Tongue broad, 

 depressed, fleshy, rounded in front and free around edges. Maxillary 

 reaches about opposite middle in snout length. Maxillary barbel 

 slender, depressed basally, reaches opposite second dorsal ray base. 

 Outer mental barbels slightly extended beyond pectoral origin. 



Fig. 11. — Rhamdia holomelas rupununi Fowler . (Type.) 



Inner mental barbels shorter, reach f to pectoral origin. Mandible 

 shallow, with snout slightly protruded in front. Internasal spaces 

 subequal, anterior nostril near front edge of snout and posterior at 

 last third in its length. Interorbital narrow, osseous area restricted, 

 and cutaneous supraorbital region elevated to produce concave 

 appearance. Surface of head smooth, covered with skin. Opercle 

 broad. Occipital process short, well separated from dorsal. 



Gill-opening extends forward opposite front pupil edge. Gill- 

 rakers 5+ 13, slender, curved, lanceolate, little longer than filaments, 

 or If in eye. Isthmus broadly convex. 



Body covered with smooth skin, without any rugose areas. L, 1. 



superior at first, becomes median after ventrals, complete and 



continuous on caudal base, not branched. 



Dorsal origin about first third in space midway between snout 

 18 



