84 L. Agassiz on the Ichthyological Fauna of Western America. 
from the posterior side, 6 and 6’ being two lateral views of the 
lower teeth, and ¢ a view of an upper toot 
The scales are considerably longer than high, with a rather 
prominent posterior — numerous radiating furrows upon 
the anterior and poster r fields, me across the lateral fields; 
the concentric ridges of, the dee field are not only broader 
that those of the other fields, but instead of running parallel to 
the margin of the scales they are curved in concentric gothic 
arches between each two radiating furrows. Heckel mentions 
this genus under the name of Rhytidostomus, but Rafinesque’s 
name Cycleptus has the priority. Properly it ought to be called 
Leptocyclus, according to its etymology, (see my Nomenclator 
eae Index Universalis, p. 109,) but under this form no- 
ould recognize it as Rafinesque’s name, I shall therefore 
not ae rhe change. I must leave it doubtful whether we have 
more than one species of this interesting genus. I have before 
me specimens from Cincinnati, kindly forwarded to me by Prof. 
Baird, and others from St. Louis, Missouri, for which 1 am in- 
indebted to Dr. George Engelmann, but they differ so much in 
size, those from Ohio being young and those from Mississippi 
rather large, that I am unable to decide whether the differences 
they exhibit are specific or merely characteristic of theirage. In 
the St. Louis specimens the peduncle of the tail is shorter, the 
lobes of the caudal fin broader, the scales of the sides of the body 
less pointed behind and the caudal fin not so deeply forked. 
Should these differences prove specific, the name of Cycl. nigres- 
cens proposed by Rafinesque may be retained for the St. Louis 
type, and that of C. elongatus for that of Cincinnati; should they 
the same, the name elongatus, applied by Lesueur for his Ca- 
tostomus elongatus, having the priority over that of Rafinesque, 
must be preserved for bot h. 
The preceding descriptions show that instead of four species of 
Catostomi with a long dorsal, mentioned in Dr. Storer’s Synopsis 
of the fishes of North America, as Catostomus elongatus and Bu- 
balus and Sclerognathus Cyprinus and Cyprinella, we have not 
than four distinet genera of this type: Carpiodes, Bubalich- 
thys, Ichthyobus and ‘Cyeleptus, numbering together sixteen or 
seventeen species, fourteen of which I have been able to deseribe 
and a to compare with one another, having specimens 
my own collection. 
It isa I fect worth mentioning that the whole of this type is 
wanting in the waters of the Pacific slope of our continent, from 
which indeed a ee” species of the genus Catostomus proper 
far. 
known th 
Moxostoma, Raf. 
ost authors refer the species of this genus to Catostomus 
proper. DeKay however refers them to Cuvier’s genus Labeo, 
