

GENUS CATOSTOMUS. 153 



The jaw-bones are very feeble, the intermaxillary being reduced to a 

 tbin lamella, which does not descend to the middle of the maxillary. 

 The anterior part of the mandible is horizontal, thin and slightly dilated. 

 The apophyses of the four anterior vertebra are very strong and long." 

 (Gu^THER, Cat. Fishes Brit. Mus. vii, 13.) 



This genus as at present restricted comprises three well-marked 

 groups, which may be accepted as subgenera, under tbe names Catosto- 

 miiSj DccadactyhiSj and Eypcntelium. One of these groups, Hypentelium, 

 has been usually considered as a distinct genus, on account of the dif- 

 ferences in the form of the head and in the squamation. These differ- 

 ences are, however, individually of subordinate value, and should 

 probably be held to designate a subgeneric section, rather than a 

 distinct genus. 



The group Decadactylus as here given is nearly equivalent to Minomus 

 and Catostomus of Girard, while our Catostomus is Girard's Acomus. 

 The type of Catostomus, as restricted by Agassiz, prior to Girard being 

 Cyprinus catostomus Forster, oi:e of the small-scaled group, the name 

 belongs properly to that group, and Acomus is a simple synonym. 

 Decactylus Eafiuesque was not originally defined in any very tangible 

 way, inasmuch as its author included in it species of Myxostoma and 

 Cycleptus. As, however, it was intended for 10-rayed species, and as one 

 among those origiuallj* placed in it was C. teres (as C. bostoniensis), the 

 the name Decactylus (Decadactylus) may be used instead of Minomus as 

 a designation for the subgenus to which C. teres belongs. 



Tbe genus Catostomus is, next to Myxostoma, the most rich in species. 

 It is much the most widely distributed of the genera of Suckers, some of 

 its members abounding in every river of Xorth America, and one of them 

 being found in Asia. 



Generic Characterizations. 



"CATOSTOMUS LeSueur, 1817. 

 "Back with a single fin. 



"Gill-membrane three-rayed. 

 "Head and opercnla smooth. 



'Jaws toothless and retractile. 



'Mouth beneath the snout ; lips plaited, lobed, or cartmcnlated, suitable for sucking. 

 Throat with pectinated teeth. 



'The species which are here described are all possessed of the following general 

 Jters : 



'Body. The body in general is elongated and varied in its form. 



'Scales. The scales in almost all the species are marked with radiated lines, and 



ibriated on their edges ; their form more or less rhomboidal or roundish. 



