94 



PROCEEDINGS OF THE ACADEMY OF 



Family SIL URIDJE. 



Subfamily PIMELODIN^E. 



Rhamdia dorsams Gill. 



B. 6. P. I. 8. V. 6. D. I. 6. A. 9. 



The body is moderalely slender; the height rather exceeding a fifth of the 

 length (exclusive of the caudal), while the height of the caudal peduncle is 

 about an eleventh. The head forms rather more than a fourth of the length, 

 and is about three fourths as wide as long, or more than twice as wide as the 

 interocular area ; the skin is moderately thick and smooth ; and the supraoc- 

 cipital spine is pointed and extends beyond the vertical of the bony opercular 

 margin. The eyes enter about eight limes in the head's length, are entirely 

 in the anterior half of the head, and are about equally distant from each other 

 and the middle of the upper jaw. The upper jaw projects but little beyond 

 the lower. The intermaxillary band of teeth is widest near the angles, where 

 it is truncated and obtusely angulated, and rather narrowest at the middle ; 

 the greatest width exceeds a sixth of the length. The intramandibular flaps 

 are considerably wider than the dentigerous bands. The maxillary barbels 

 extend to or beyond the middle of the ventrals ; the external mandibular 

 extend beyond, and the internal nearly to, a line with the bases of the pec- 

 torals. 



The dorsal fin is oblong, the longest rays equalling the distance from the 

 second to the axilla. The adipose fin is contained between three and four times in 

 the length. The pectorals terminate under the second or third dorsal ray, and 

 are not much larger than the ventrals. The porus axillaris is very minute. 



The color is dark brown. The dorsal has the usual broad clear basal band. 



SORUBIMICHTHYS ORTONI Gill. 



B. 14, 14 D. I. 6. A. 13. C. iii, I, 1, 8, I, iv. P. I. 10. V. 6. 



The head forms rather more than a third of the length, exclusive of the 

 caudal fin; the outline above is oblong, convex in front; the width is less 

 than half its length, and the width between the orbits less than a third ; the 

 hinder margin of the orbit is midway between the snout and opercular flap ; 

 the profile is perfectly straight. The dentigerous area of the upper jaw pro- 

 jects almost entirely beyond the lower jaw, and equals the chin or two diame- 

 ters of the orbit; it is uninterrupted, except behind at the middle, where 

 there is a broad but shallow triangular sinus; the palatal bands externally 

 describe half an ellipse, and are only interrupted at the middle by a linear 

 furrow widening backwards into a hastiform sinus ; their antero-internal an- 

 gles are, however, rounded. The maxillary barbels extend to the anal ; the 

 external mandibular terminate at some distance from the pectoral fins, ami 

 the internal are less than the width of the upper jaw. 



The dorsal spine is unarmed, or scarcely rough behind ; the adipose fin ob- 

 liquely truncated, shorter than the anal and nearly coterminal with it; the 

 pectorals terminate nearly under the last dorsal ray, and in advance of the 

 ventrals, than which they are considerably larger. The caudal is shorter than 

 the head, the lobes are acutely prolonged, and the upper lobe is somewhat 

 larger than the lower. 



The color is ashy with a broad silvery band bounded above by a narrower 

 blackish one, which is bifurcated in front, and below by a still narrower one, 

 or rather a series of partly confluent spots ; numerous spots, generally much 

 smaller than the eyes, cover the entire upper portions of the body and head, 

 as well as the dorsal, adipose, and pectoral fins. 



This species is among those described most closely related to S. Artedii 

 (Platystoma Artedii Gthr. = Mystus No. 6 Artedi), but the length of the bar- 

 bels and coloration at once distinguish it, and still more decided differences 



[Aug. 



