300 



U. S. p. E. R. EXP. AND SURVEYS — ZOOLOGY — G^iNERAL REPORT. 



broad when expanded, and, when directed backwards, their extremities remain very far from the 

 insertion of the ventrals. 



D 2, 8 + 1 ; A 2, 8 + 1 ; C 0, 1, 9, 8, 1, 5 ; V 1, 9 ; P 16. 



The scales, which are of moderate development, are very thin, much deeper than long, sub- 

 circular, sub-quadrangular, or undulated upon their periphery. Numerous radiating furrows 

 may be observed upon their posterior half, and sometimes also upon the lateral sections, and 

 either directed posteriorly from the sides, or else sideways. 



The color of the upper regions is olivaceous, whilst the lower part of the flanks and the belly 

 are whitish or yellowish, with a metallic reflect. The fins are unicolor ; the caudal and dorsal, 

 greyish ; the others yellowish. 



List of specimens. 



3. PTTCHOCHEILUS EAPAX, Grd. 

 Plate LXV. 



Spec. Char. Body elongated, sub-fusiform in profile. Head rather small and tapering forwards, contained four times and 



a half in the total length. Posterior extremity of the maxillar bone extending to a vertical line intersecting the anterior rim 

 of the pupil. Eye sub-elliptical ; its diameter entering about eight times in the length of the side of the head. Anterior margin 

 of dorsal fin somewhat nearer the fork of the caudal ihan the extremity of the snout. Fins well developed. Dark brownish 

 black above ; whitish beneath. 



Stii.—Plychochtilus rapax, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 209. 



This is also a large species, differing from P. grandis by a proportionally shorter body, a 

 more advanced position of the ventral fins and by much smaller scales on the dorsal region in 

 advance of the dorsal. The dorsal fin, compared to its length, is less elevated, although higher 

 than long. The inferior limb of the pharyngeal bones is not so long and slender, and there are 

 but four teeth upon the main row, instead of five. The teeth and bones are stouter. The 

 upper margin of the dorsal fin is nearly linear, somewhat sub-convex. The same is true with 

 reference to the anal fin, the anterior margin of which being nearly equidistant between the 

 tip of the inferior lobe of the caudal and the base of the pectorals. The ventrals are posteriorly 

 rounded, not reaching the vent. The pectorals are likewise broad and rounded ofi", and their 

 extremities, although far from reaching the origin of the ventrals, do, nevertheless, come a 

 great deal nearer to it than in F. grandis. 



D 2, y -f 1 ; A 2, 8 -f 1 ; C 5, 1, 9, 8, 1, 6 ; V 1, 9 ; P 18. 



The scales on the middle of the flanks are of moderate development, and rather small 

 elsewhere. They are very thin, deeper than long, sub-circular, irregular in their outline, with 

 radiating furrows upon tlieir posterior half, sometimes upon their entire surface. The lateral 

 line is nearly median. All the upper surface and sides of the head, as far as a horizontal line 

 drawn from the edge of the upper jaw direct to the caudal fin, which line passes below the 



