FISHES C YPRINID AE CATOSTOMI. 



217 



of the side of the head. The anterior margin of the dorsal is nearer the tip of the central rays 

 of the caudal than the extremity of the snout. The base of the anal enters but eleven times in 

 the total length. The insertion of the anal is comparatively more anterior than in M. conoce- 

 phalus, and that of the ventrals also. We count the rays as follows : 



D 2, 8 + 1 ; A 2, 8 + 1 ; 6, 1, 9, 8, 1, 6 ; V 1, 9 ; P 18. 



The dorsal scales appear to be sub-circular, deeper than long ; whilst those of the lateral 

 line and of the abdominal region are longer than deep and somewhat irregular in their outline. 



The largest specimen, from which the accompanying figure was made, measures eighteen 

 inches and a half in total length. 



The one received from Dr. Ayres is smaller, measuring but sixteen inches. Both were 

 purchased in the market of San Francisco, and are reported as having been caught in the San 

 Joaquin river. 



References to the figures. Plate XLVII, fig. 1, represents Mylopharodon robustus, reduced in 

 size. 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. 



List of specimens. 



TRIBE OF CATOSTOMI 



The distinguishing characters of the suckers or Catostomi as a peculiar group consist, in 

 the first place, in the structure and position of the mouth, which is surrounded with large and 

 fleshy lips, situated under the protruding snout, and in the absence of barbels. The pharyngeal 

 bones are sickle-shaped, varying in the curvature of the dental portion and also in the inferior 

 branch. The teeth are numerous / disposed upon one single series ; the inferior ones being 

 longest, the others diminishing in size upwards. To use the expression of Heckel, the teeth 

 are pectiniform (Denies pectiniformis ) , that is, arranged like a comb. The anterior margin of 

 the dorsal fin is situated in advance of the insertion of the ventrals. 



Modifications of these characters, associated with others, will furnish the means of distin 

 guishing the genera. 



STN. Catostomi, AGASS. in Amer. Journ. of Sc., 2d series, XIX, 1855, 73. GRD. in Proc. Acad. Nat. Sc. Philad., VIII, 

 1856, 170. 



The scarcity of materials at our command will compel us to give a very brief diagnosis of 

 the generic characters to be assigned to Carpiodes. 



28 a 



