408 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



less generically, distinguished. The barbels, being only tags of skin proceeding from 

 the integument of the maxillary bones, have very little systematic value compared with 



tinned differences are those only which have induced ichthyologists to distribute them, 

 we have no hesitation in bringing the above-named genera together as closely-allied 

 members of the same subfamily. Ahjoma was indeed placed by Dr. Girard among the 

 Chondrostomi, but he was probably led to that act by the consideration of the single 

 row of pharyngeal teeth and the absence 01 barbels, and not on account of the pres- 

 enee of a cartilaginous sheath enveloping the lower jaw. Girard has expressly stated 

 that the sheath is not one of the essential characters of the -roup as understood by 

 him. Bleeker was therefore incorrect in placing that -enus in a group of which the 

 presence of the cartilaginous sheath was the principal distinction. 



I he following appear to be the distinctive characters of the genera above enunier- 



ventraljins are nwhr the anterior ,„,,,■ of the dorsal fin. The scales are large, there being 

 about forty in the typical species along the lateral line. The center of the eye is 

 behind the middle of the head. There are well-developed maxillary barbels. 



' The genus Sanotilns of Rafinesque lias a head much like that of the Gohiones, 

 but it is usually larger, and declines less toward the snout. The bases of the ventral 

 fius mv more anterior, being almost entirely in adranee of the W sal fin. The scale< 

 are comparatively small. The eves are mostly or altogether in the anterior half of the 

 head. The barbels are also somewhat smaller. The genus Lencosomus of Meckel and 

 Girard is strictly identical with this. 



In the genus Po f/ oniehth>,.s as now restricted, the head is small, compressed, and 



fins are mnhr the ,nkhlh> of the dorsal, the scales are of moder- 

 . The eyes are almost entirely situated in the anterior half of 



i.idl 



id. Th 





,1, the width at the occiput being only about a third less than the naked 

 species of VlaUj, f obh> is known. Numerous specimens were collected on 



PLATYGOBIO COMMUNIS, Gill. 

 Synonymy. 



MlNb/ ',""" U, ' M '"' * ; ■' ( ' ' 'i I'i-h.-. .. ~. [,-, ,,.-.»|. n Pi, ■«,,.. lmgs of Academy of 

 Mices, vol. vni, p. 1- !>:,.;: Guard. Iclitliyologj „f Pa, ill, Uailma.l R.-ports, p. 247, pi. lv. 



' gradually decreases in breadth from the 





I fin, is slightly curved 



