216 



U. S. p. R. R. E.\P. AND SURVEYS — ZOOLOGY — GENERAL REPORT. 



1. MYLOPHARODON CONOCEPHALUS, Grd 



Plate XLVI, Fios. 



-8. 



Spec. Char. — Head sub-conical. Posterior extremity of maxillar bone not extending as far as the anterior rim of the orbit. 

 Eye well developed. Pectoral and ventral fins of moderate size. Vertical fins well developed. Anal and dorsal much deeper 

 than long. Base of anal entering twelve times and a half in the total length. Brown above ; whitish beneath. 



Silt.— Gila conocephala, B. & G.in Proc. Acad. Nat. Sc.Philad. VII, 1854, 134. 



Mylopharodon conocephalus, Grd. in Proc. Acad. Nat. Sc. , Philad. VIII, 1856, 1G9. 



There was but one specimen of this species collected, ahout seven inches and a half in length. 

 Its general shape is sub-fusiform, compressed ; the back slightly convex from the nape to the 

 posterior margin of the dorsal fin. The head is sub-conical and contained exactly four times in 

 the length, the caudal fin excluded. The mouth is comparatively large, although the posterior 

 extremity of the maxillar bone does not quite extend to the anterior rim of the eye ; the snout 

 being prolonged, and the cleft of the mouth nearly horizontal. The eye is sub-circular and its 

 diameter contained five times and a half in the length of side of head. The anterior margin of 

 the dorsal is nearer the end of snout than to the tip of the central rays of the caudal. The 

 furcated caudal participates of the slender appearance of the body. The origin of anal is 

 situated behind the base of the dorsal. The insertion of the veatrals is situated in advance of 

 the anterior margin of dorsal ; their tip reaching the anus. 



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



The scales are sub-circular and of medium size ; the lateral line forms an open curve along 

 the sides, the convexity of which is downwards. 



The upper regions of body and head are brown ; the sides yellowish ; and the abdomen 

 whitish. 



Beferences to the figures. — Plate XLVI, fig. 5, represents Ilylojjharodon conocephalus, size of 

 life. Fig. 6 is 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..MYL0PHAR0D0N ROBUSTUS, Ay res. 

 Plate XLVII. 



Spec Char.— Upper surface of head very declivous ; snout tapering, almost wedge-shaped. Posterior extremity of max- 

 illary extending to a vertical line drawn across the anterior rim of tlio orbit. Eye of medium size. Pectoral and ventral fins 

 broad and stout. Anal nearly as large as the dorsal. Ground color olivaceous, darker above than below. 



Sin .—Mylopharodon robustus, Ayres, in Proc. Cal. Acad. Nat. Sc, I, 1855, 33.— Grd. in Proc. Acad. Nat. Sc. Philad. 

 VIII, 1856, 1C9. 



Tiiis species is closely allied to the preceding one. The head is contained four times and a 

 half in the total length. The diameter of the eye entering nearly eight times in the length 



