298 



U. S. P. R R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



of the caudal than the isthmus ; its own base entering from thirteen to fourteen times in the 

 entire length. The origin of the ventrals takes place opposite the anterior margin of the dorsal, 

 hence nearer the insertion of the caudal fin than the extremity of the snout. These fins are 

 sub-ovate in their outline, posteriorly rounded off, and when leaning on the abdomen their 

 extremities do not extend as far as the vent. The pectorals are sub-ovate also, although less 

 regularly so than the ventrals. The distance which separates their posterior extremities from 

 the insertion of the ventrals is less than their own length. 



D 2, 9 + 1 ; A 2, 8 + 1 ; 07, 1, 9, 8, 1, 6 ; V 1, 8 ; P 16. 



The ground color is olivaceous, the sides and the back being nearly black or brownish black, 

 from the number of confluent maculae and dots. The inferior region is greyish white. The 

 fins themselves are blackish upon an olivaceous ground. The sides and upper part of the head 

 are likewise brownish black. 



List of specimens. 



PTYCHOCHEILUS, Agass. 



GEN. CHAR Body elongated, sub-cylindrical, and compressed. Head elongated also ; mouth deeply cleft, but no barbels 

 upon its angle. The snout overlaps the lower jaw, although the mouth remains horizontal and sub-terminal. The eye is o* 

 moderate size, and so with the isthmus. The ventral fins are inserted somewhat in advance of the anterior margin of the dorsal. 

 The caudal is furcated and shorter than the head. The scales are of medium size ; the lateral line being nearly median. The 

 pharyngeal bones are long and slender, slightly expanded upon their convexity, with the inferior limb much more slender than 

 the upper. The teeth are of the raptatorial kind, of the hooked type without grinding surface, sub-conical, slightly hooked, 

 and disposed upon a double series of two and four or five, thus : 2 | 4 4 | 2, or 2 | 5 5 | 2. 



Six. Ptychocheilus, AGASS. in Amer. Jour, of Sc. 2d Ser. XIX, 1855, 227. GRD. in Proc. Acad. Nat. Sc. Phiiad. VIII, 

 1856, 208. 



By their general appearance, the species of this genus remind us of both Mylopliarodon and 

 Myloclieilus. Besides the cleft of the mouth, which is proportionally greater, they differ from 

 the latter two genera by their system of dentition, which belongs to a quite different type. 



I. PTYCHOCHEILUS OREGONENSIS, Grd. 

 PLATE LXIV, FIGS. 59.* 



SPEC. CHAR. Body sub-fusiform in profile. Head rather small, elongated ; contained four times and a half in the total 

 length ; snout slender. Mouth deeply cleft ; posterior extremity of maxillary extending to a vertical line intersecting almost 

 the anterior rim of the pupil. Eye of moderate development ; its diameter entering about five times in the length of the side 

 of the head. Anterior margin of dorsal fin equidistant between the extremity of the snout and the fork of the caudal. 

 Pectoral and ventral fins rather small. Back and upper surface of head dark reddish brown ; flanks and belly white, with a 

 silvery tint. 



SYN. Cyprinus (Leuciscus} oregoncnxis, RICHARDS. Faun. Bor. Amer. Ill, 1836, 305. 



PtychocJieilus gracilis, AGASS. & PICK, in Amer. Journ. of Sc. 2d Ser. XIX, 1855, 229. 

 Ptychocheilus oregonensis, GRD. in Proc. Acad. Nat. Sc. Phiiad. VIII, 1856, 209. 



*By error on the plate, Ptychocheilus gracilis, Grd. 



