86 L. Agassiz on the Ichthyological Fauna of Western America. 
and finally vanishes entirely in specimens of about three inches 
in length. Such a young specimen of our eastern species 
been described by Lesueur as Catostomus vittatus. The body of 
Moxostoma is elongated aud somewhat compressed; though 
stouter than that of the Ptychostomus and Catostomus proper ; 
its greatest depth is above the ventrals. 
‘The head is small; the small mouth opens obliquely for- 
wards and downwards: when open the lower jaw is quite prom- 
iuent. The lips are small and transversely ridged ; the lower one 
is slightly bilobed. 
The dorsal is over the ventrals ; its length considerably exceeds 
its height in the males; in the females these dimensions are more 
nearly equal. .'The pectoral and ventrals are more pointed and 
longer in the males than in the females. The lower margin © 
the anal fin is bilobed in the males, while in the females it is sim- 
ply ron aoe ; in both sexes, the anal, when bent backwards, 
reaches the c 
‘The phar nineacandl bones have a greater resemblance to those of 
the genus Ichthyobns, than to any other of the tribe of Catos- 
tomi; the symphysis however i is shorter, and the teeth are neither 
so minute, hor so numerons ; they increase also more rapidly in 
size fram above downwards, and are more strongly curved in- 
wards; their cutting edge is slanting outwards, the innermost 
edge rising into an acute point, which is more prominent in the 
middle and upper teeth, than in the lower ones. Fig. 5, a, repre- 
sents the right pharyngeal of icantins oblongum, 6 one of the 
lower teeth in profile ; ¢ another in the same position ; d the same, 
from the sharp side. 
Former investigators, unconscious of the marked differences 
which exist in this genus between individuals of different sexes 
aud ages, in different seasons of the year, have described a num- 
ber of nominal species, which may now safely be reduced to their 
— relations. DeKay, in his Natural History of the State of New 
, describes the species so common in the Eastern States, un- 
ine no fewer than five different names, as Labeo gibbosus, Labeo 
elegans, Labeo esopns, Labeo oblongns, aud Catostomus tubercu- 
latus, and mentions it a sixth time under the name of Catostomus 
Vitlatus, given to the young by Lesueur. or Storer in his synop- 
sis of the fishes of North America, has it under five ditierent 
names, as Cat 1s ibbosus, oblo us, techie, esopus, 
vittatus. The oldest ae applied to this. fish being that of C 
