244 



U. 8. P. R. R EXP, AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



References to Ihe figures. — Plate LIV, fig. 5, represents Argp-eus dulcis, size of life. Fig. r>, 

 a scale from the dorsal region. Fig. 7, a scale from the lateral line. Fig. 8, a scale from the 



abdominal region. 



List of specimens. 



2. ARGYEEUS NUBILUS, Grd. 



Spec. Char. — Head rather small, constituting llie fifth of the entire length. Mouth small, and barbel inconsj)icuous ; lips 

 cartilaginous. Eye moderate sized, sub-circular ; its diameter entering five times in the length of the side of the head. Anterior 

 margin of dorsal fin nearer the extremity of the snout than the tip of the middle rays of the caudal. Insertion of ventral fins 

 cqui-dislant between the angle of the mouth and the base of the caudal. Blackish brown above ; dirty or dull while beneath. 



Syn.— .Jig-i/rcus nuhilus, Grd. in Proc. Acad. Nat. Sc. Pliilad. VIII, 1856, 186. 



This is a very characteristic species. The head is very small, and the body, fusiform in shape 

 and compressed, is thick and swollen upon its middle. The tail again is rather slender. The 

 snout is sub-conical, though not more protruding than in the preceding species ; the mouth is a 

 good deal smaller than in the latter, and its barbels less conspicuous. The head constitutes 

 about the filth of the entire length. The eye is moderately developed and sub-circular in shape; 

 its horizontal diameter is contained about five times in the length of the side of the head. The 

 dorsal, caudal, and anal fins are of but moderate development, the pectorals and ventrals being 

 rather small. 



D 2, 8 ; A 2, 7 ; C 5, 1, 9, 8, 1, 6 ; V 8 ; P 12. 



The number of rays in the fins does not materially differ from that of the preceding specifes ; 

 in both, the anterior two rays of the dorsal and anal fins are mere rudiments. 



The scales are sub-ovoid in their outline, with radiating furrows upou their entire peripliery. 



The color above is blackish brown, with a purplish hue along the middle of the flanks ; the 

 inferior regions are of a soiled wliite or yellowish brown. The upper surface of the head and 

 upper half of the bides, including the eye, is deep black ; inferiorly it is whitish or yellowish 

 white. 



Specimens four inches in total length were observed. 



List of specimens. 



