74 L. Agassiz on the Ichthyological Fauna of Western America. 
ently characterised by Rafinesque. In order to ascertain beyond 
a question the generic value of these characters | have examined 
the pharyngeals of every one of the species described in this 
bly found that within the limits within which the genera are 
circumscribed here, they present a peculiar type for each genus, 
reproduced in the different species with slight variations in the 
size and proportions of the tecth, the strength of the arch aud 
the length of its symphysis. 
Thus far the whole tribe of Catostomi must be considered as 
parece setcheiaively to North America, the true relations of the 
Catostomus Tilesii, founded by Valenciennes, upon the descrip- 
tion of the Cyprinus rostratus, from Northern Asia, by Tilesins 
being still doubtful, or wanting at least the only confirmation 
acceptable in our days, that is based upon a direct comparison of 
original specimens. Catostomi are found as far south as Texas 
and along the alana boundaries of Mexico, as is shown by the 
descriptions of several species published by Messrs. Baird and 
Girard in the Proceedings of the Academy of Natural Sciences 
of Philadelphia for 1854, but 1 have been unable to ascertain 
whether they inhabit the waters of Cuba 
It is a very interesting fact that while ‘America has no native 
representation of the tribe of Carps, some of. its Catostomi, the 
Carpiodes, Ichthyobus and Bubalichthys, remind us strongly by 
their external appearance of the true Cyprini of the old world, 
whilst others, the Cycleptus and Moxostoma resemble more the 
Borbus of Europe, Asia and Africa and the Tinca of Enrope, 
which are also entirely wanting in America, and still others, the 
Catostomi proper have not even analogous representatives in the 
eastern continents. 
Carpiodes, Raf. 
1. The body is very high and strongly compressed, the narrow 
ridge of the back forming the outline in front of the dorsal is 
very much arched, and regularly continuous downwards with the 
rather steep profile of the head. 
head is short, its height and length differ but little. The 
snout is short and blunt. The small mouth is entirely inferior, 
and surrounded by narrow thin lips, which are more or 
transversely folded. The lower jaw is short and broad. 
The pharyngeal bones of Carpiodes are remarkably thin, com- 
pressed laterally, with a shallow furrow along the anterior margin 
on the inside, and another more central ove ou the outline of the 
arched ‘surfaces ; the teeth are very small, compressed, equally 
thin along the whole inner edge of the bone, forming a fine comb- 
of minute serratures ; their cut — rises above the 
