L. Agassiz on the Ichthyological Fauna of Western America. 231 
When shut, the rays of these fins are brought close together, but 
do not overlap each other as is the case with the rays of the dor- 
sal and anal and with the middle rays of the caudal. The dorsal 
has a narrow base, as has also the anal, both fins having the same 
structure, differing only in size. There are two small rays in ad- 
vance of the long ray of the dorsal, followed by seven branching 
rays the last of which, however, is a double ray. e anal has 
precisely the same number of rays. The caudal is large, furcate, 
and has eight smaller rays along the upper and lower margin ; 
then, on each side, a large simple ray. The upper and lower 
lobes are apparently equal; there is, however, one ray more in 
the upper lobe, that is to say, nine above and eight below. The 
inner ones overlap each other when the fin is shut. The scales 
are of medium size and have the common appearance of Leucis- 
cus scales. The lateral line slightly bent downwards behind the 
operculum, follows about the middle of the side. The intestine 
has twice the length of the abdominal cavity, and is a simple 
tube tapering from the stomach backwards. The air bladder as 
usual, consists of two divisions with a tube opening into the pha- 
tynx. The humerus forms a widely rounded angle above the 
pectorals, 
Fig. 18, a, represents the right pharyngeal from behind, 4 from 
Within so as to show the crown of the teeth from above, ¢ repre- 
sents the same in profile to show the insertion of the teeth; @ and 
d’, represent the same tooth, the second above the symphysis, from 
two sides showing how much it is compressed ; ¢ is a side view 
of the outer or upper tooth of the main row. 
Mylocheilus lateralis, Agass. & Pick. 
Greenish blue above with a reddish line upon the sides. Upper 
fin greenish. The edge of the caudal reddish. Pectorals and 
ventrals orange. The horny plate of the mouth is of a brown- 
Orange, : 
Caught in the Columbia River at Fort Vancouver in Oregon. 
(To be continued.) 
