- 222 L. Agassiz on the Ichthyological Fauna of Western America. 
and e, one hooked tooth in profile. The scales of this genus are 
also very peculiar; their longitudinal diameter is much shorter than 
the vertical, as in Plargyrus, and the centre of radiation is much 
nearer to the anterior, than to the posterior margin ; the concen- 
tric ridges of the ornamental layer of the outer surface are close 
together, and only interrupted by radiating furrows upon the pos- 
terior and lateral fields of the scales. e tubes of the lateral 
line short, broad and curved downwards upon the middle of the 
posterior fields of those scales. 
Hyborhynchus, Agass. 
In respect to the arrangement of the scales, and the structure, 
position and form of the fins, this genus does not differ fro 
imephales ; it is chiefly distinguished by characters of the head 
and the pharyngeals. ‘The head is long and flattened above ; 
the profile descends suddenly on reaching the nostrils, forming @ 
very blunt, gibbous snout, (whence the generic name Hyborhyn- 
chus). The mouth is small, beneath the snout, and cut horizon- 
tally. The lower jaw is flat, broadly rounded in front and 
shorter than the upper jaw. The sides of the head are vertical 
phales, with a narrow, flat grinding surface and a slightly arched 
t ‘ig. 13, a, represents the right pha- 13, 
long, and the centre of radiation very 
forwards as in Pimephales; but the ra- 
diating furrows are not so numerous, and the tubes of the lateral 
