GENUS CATOSTOMUS. 153 



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

 thin kimella, 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 vertebrae are very strong and long." — 

 (GuNTHER, Cat. Fishes Brit. Mus. vii, 13.) 



This genus as at present restricted comprises three well-marked 

 groui)S, which may be accepted as subgenera, under tbe names Catosto- 

 omis, Dccadactylus^ and Eypentelium. One of these groui>s, 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 Becadactylus as here given is nearly equivalent to Minomns 

 and Catostomus of Girard, while our Catostomiis 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 Acomiis is a simple synonym. 

 Decaciylus Rafinesque 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 lO-rayed species, and as one 

 among those originall}^ placed in it was C. teres (as C. hostoniensis), the 

 the name Decaciylus {Becadactylus) may be used instead of Minomus as 

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



The 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 ISTorth America, and one of them 

 being found in Asia. 



Generic Characterizations. 



''Catostomus Le Sueur, 1817. 



"Back with a single fiu. 



"Gill-membrane three-rayed. 



"Head and opercula smooth. 



"Jaws toothless and retractile. 



'•Mouth benea'.h the snout ; lips i^laited, lobed, or carunculated, suitable for sucking. 



" Throat with pectinated teeth. 



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

 characters : — 



"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 

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



