FISHES — SILURIDAE — PIMELODUS OLIVACEUS. 



211 



5. PIMELODUS LUPUS, G r d . 



Spec. Char. — Body subfusiform, compressed ; liead depressed, broader tlian deep, anteriorly tapering, and constituting the 

 fourth of the total lengtli. Mouth moderate size, upper jaw tlie longest. Maxillar barbel extending to about the middle of 

 the pectoral fin. Eye sub-elliptical, of medium size, its diameter entering nearly seven times in the length of the side of the 

 head, and about three times in the intcrocular space. Dorsal spine very obtusely denticulated towards its upper extremity, 

 pectoral spine very conspicuously so. Caudal fin moderately furcated. Base of anal fin shorter than the head, and contained 

 nearly five times in the total length. Blackish brown above, dull white or light slate colored beneath. 



This species resembles somewhat P. vulpes (figured ia the Rep. to the U. S. and Mexican 

 Boundary Commission) in its general physiognomy, differing, however, from the latter by a 

 proportionally shorter head. It belongs to that division of the genus in which the body and 

 head assume a rather slender appearance. It is, however, more compactly built than most of 

 its allies. The rays of the fins are : 



Br. VII: VII ; D I, 6 ; A 24 ; C 10, 1, 8, 7, 1, 10 ; V 8 ; P I, 9. 



The insertion of the ventrals is nearly eq[uidistant between the extremity of the snout and the 

 insertion of the caudal. These fins themselves are broad, overlapping the vent and reaching the 

 anterior margin of the anal when stretched backwards alongside the abdomen. The nasal 

 barbels are slender, and do not extend as far as the posterior rim of the orbit. 



The upper region is dark brown with a metallic reflect, the head beneath being dull white and 

 the abdomen light bluish or slate colored. 



List of specimens. 



6. PIMELODUS OLIVACEUS, G r d . 

 Plate XLI, Figs. 1—3 ; and Plate XLII. 



Spec. Char. — Body sub-fusiform, compressed. Head very mrch depressed and tapering, constituting about the fifth of tha 

 whole length. Mouth small ; upper jaw the longest. Maxillar barbel extending to the middle of the pectoral fin. Eye large, 

 sub-elliptical ; its diameter contained five times and a half in the lengtb of side of head, and about twice on the interocular 

 space. Dorsal spine very finely serrated posteriorly; pectoral spine very strongly so. Caudal fin deeply furcated. Olive- 

 brown above ; olive-white beneath. 



The body and head have a rather slender appearance. It is allied to P. coelurescens, from 

 which it appears to differ by several minor characters, which we must refrain for the present to 

 express comparatively in words, not having before us the specimens of the typical P. coerulescens, 

 preserved in the museum of the Smithsonian Institution, but not available at the time these 

 pages were passing through the press. We have counted the rays upon specimens from the 

 Yellowstone river, and found them to be as follow : 



Br. VII : VII ; D 1, G ; A 26 ; C 10, 1, 8, 7, 1, 9 ; V 8 ; P I, 8. 



The nasal barbel is slender and rather short, and when stretched along the surface of the 

 head not extending as far posteriorly as the hinder rim of the orbit, but averaging about 

 between the latter and the pupil. 



