i | Opn emt 
L. Agassiz on the Ichthyological Fauna of Western America. 93 
more rapidly in size from above downwards, so that those of the 
middle of the arch are already of the same cast as those of the 
lower part of the comb; their crown is blunt and the inner edge 
rises into a blunt cusp. Fig. 8, a, represents the right pharyngeal 
a 
of Catostomus communis, } being one of the lower teeth, ¢ one 
from the middle of the arch and d a side view of the same. 
_ This genus has representatives over a much greater geograph- 
ical area than any other of the tribe, some are found even as far 
north as the fur countries of North America, others iu Lake Su- 
perior ; farther south they occur in all the fresh waters of the 
United States as far as Texas and the northern boundaries of 
Mexico, whence Mr. John H. Clark has obtained several new 
Species described by Messrs. Baird and Girard in the Proceedings 
of the American Academy of Natural Sciences of Philadelphia, 
for 1854, page 27. I have myself received a new species from 
N. Mexico, through the kindness of Dr. Henry of the U. S. Army 
and another from Georgia through Prof. J. LeConte. Sir John 
Richardson mentions their occurrence in the Columbia River. I 
have myself received a new species from San Francisco, Cali- 
Catostomus from the old world. As the species of this genus are 
Closely allied to one another and their distinguishing characters 
could not be plainly illustrated without figures, I will not enter 
Into more details about them for the present and limit myself to 
enumerating them and describing the species from San Francisco. 
rhe first species known is that which Lesueur has called Ca- 
tostomus Hudsonius, the Cyprinus Catostomus of Forster. Next 
Richardson (my Cat. Aurora), an entirely different species. There 
are however still some difficulties about these northern species to 
be Solved, as it remains doubtful whether there are three or four 
Or only two species ranging from the great Canadian Lakes north- 
ward. [ am unable to find any difference between Catostomus 
| ently admitted. Catostomus Clarkii and Ca- 
tostomus plebeius, B. & G., are distinct species. 
