228 L. Agassiz on the Ichthyological Fauna of Western Amer ica 
when the mouth is open. The lower lip is also very fleshy 
‘around the symphysis of the two branches of the lower jaw, and 
presents the same folds; but, upon the sides it tapers into a thin 
membranous fold deeply separated, by a furrow, from the skin 
covering the lateral branches of the lower jaw. his fold unites 
~ at the lower extremity of the intermaxillary bone, and presents 
in many respects a remarkable resemblance to the folds of the 
membrane of the lower jaw in Murenide. ‘The skin covering 
the tongue and extending between the inner sides of the two 
branches of the lower jaw, is also remarkably folded. As such 
characters occur in no other genus, 1 am well justified in consid- 
ering this as a peculiar type of the family. There is not the 
slightest indication of a tentacle at the angle of the mouth be- 
tween the intermaxillary and upper maxillary bones. 
The branchiostegal rays, three in number as usual, seem at first 
rather short, and broad, but, upon close examination it is found 
that behind and above the part of these bones which is seen eX- 
humerus, so that the branchial fissure does not extend to the side 
of the hyoid bone. : 
One of the most striking features of the fish is the great elon- 
gation of the head, which, in outline, truly resembles that of Lu- 
cioperca. ‘The body is cylindrical and slender, tapering slightly 
toward the caudal, so that the tail is very strong and powerful, 
affording another evidence of the energetic movements this fis 
ean perform. The dorsal and the veutrals are rather backwards; 
the ventrals much nearer to the anal than to the pectorals. The 
pectorals are rather large and elongated, and by no means so 
broad proportionally as the ventrals. They consist of one hard 
ray, and sixteen articulate rays, the two lowest of which are sim- 
ple. In the ventrals there is in advance one simple ray, followe 
by eight branching rays. In the dorsal, which has the same 
form as the anal, there are two small rays in advance of the large 
simple one followed by eight branching rays, the last of which 1s 
a double ray. The anal has the same structure, but there is one 
ray less. In these two fins, when shut, the rays overlap each 
other. This is also the case with the central rays of the caudal, 
in which there are nine branching rays in the upper lobe, a0 
eight in the lower. A large simple ray on each margin and seven 
or eight smalltays near the base. The lateral line considerably 
curved behind the operculum, follows at first the middle line of 
the body, but is nearer the abdomen than the back, upon the 
sides of the abdomen, and resumes its medial position upon the 
tail. The scales have the ordinary appearance of Leuciscus scales, 
‘but are rather smaller than in the common Leucisci, It is a great 
