226 



U. S. p. R. K. EXP. AND SURVEYS — ZOOLOGY — GENERAL REPORT, 



4. CATOSTOMUS SUCKLII, Grd. 

 Plate LI. 



Spec. Chab.— Head constituting the fifth of the entire length. Eye small. Mouth rather small ; lips moderately developed, 

 covered with ccmspieuoufi papillae. Isthmus of medium width. Dorsal fin as high as long; its anteiior margin somenhat nearer 

 the ineeniiin of the caudul fin than the extreuiily of tljo snout. Insertion of ventrals a little in advanee of the middle of the 

 dorsal, and equidistant between the extremity of the snout and the fork of the caudal. Posterior extremity of anal extending 

 beyond the rudimeutary rays of the caudal. Greyish olive above ; yellowiih olive beneath. 

 SvN. — Culoslomus sucklii, GitD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 175. 



The head forms the fifth of the entire length. It is sub-quadrangular, the upper stirface 

 rather sloping towards the blunt snout. The eye is small and sub-elliptical ; its horizontal 

 diameter being contained somewhat over five times in the length of the side of the head. The 

 anterior margin of the dorsal fin is equi-distant between the tip of the snout and the insertion 

 of the caudal. Its height is equal to its length, and its upper margin is slightly concave. The 

 posterior margin of the caudal is deeply emarginated, crescent-shaped. The insertion of the 

 ventrals is situated somewhat in advance of the middle of the dorsal fin. 

 D 2, 12 ; A 2, 8 ; C 5, 1, 8, 8, 1, 4 ; V 10 ; P 18. 



The scales are large and but a little smaller anteriorly than posteriorly ; they are stib- 

 elliptical in shape, longer than deep, with their anterior and posterior margins irregular, 

 exhibiting radiating grooves upon the anterior and posterior sections. The upper regions are 

 greyish olive, and the inferior regions yellowish olive. The young being of a darker and less 

 yellowish tint. 



lie/erences to the figures. — Plate LI, fig. 1, represents the adult Catostomus sucklii, size of 

 life. Fig. 2 is a scale from the dorsal region. Fig. 3, a scale from the lateral line. Fig. 4, 

 a scale from the abdominal region. Fig. 5 is the young of the same species. 



List of specimens. 



TRIBE OF CHONDROSTOMI. 



The characters of Chondrostomi, as derived chiefly from the American representatives, consist 

 in the absence of barbels ; in the position of the mouth, which is generally overhung by the 

 ujjper jaw, and sometimes both jaws are equal. The pharyngeal teeth are of the grinding 

 type {Denies masticalorii) and cultriform kind (Denies cultri/ormes), disposed upon a single 

 series, with one exception only, and that occurs occasionally in Campostoma. 1 say occasionally, 

 because in the majority of cases there is also but one single row in the latter genus. Exoghssum 

 is removed from this group, of which it has none of the characters, except the absence of 

 barbels. 



SYfi.—Chomlroslomi, Aoass. in Amer. Journ. of Sc. 2d series, XIX, 1855, 94.— Gbd. in Proc. Acad. Nat. Sc. Philad. VIII, 

 1856, 175 



