FISHES—PLEURONECTIDAE-PLEURONICHTHYS COENOSUS. 
151 
1. PLEURONICHTHYS COENOSUS, Gird. 
Spec . Chau. —Body sub-elliptical. Posterior extremity of maxillary extending to a vertical line drawn midway between the 
pupil and the anterior rim of the orbit. Origin of dorsal fin curved towards the left side of the head, and corresponding to the 
anterior rim of the upper orbit on the right side. Ground color olivaceous brown, macul :ted 
Syn. — Pleuronxchthys coenosus, Grd. in Proc. Acad. Nat. Sc. Philad. VII, 1854, 139. 
The body is sub-elliptical, the bead quite small, and the snout very short and blunt, the lower 
jaw being longer than the upper, and the mouth rather small, with its gape oblique. Minute, 
conical, and acute teeth may be observed on either side of the jaws. The posterior extremity of 
the maxillary extends beyond the anterior rim of the orbit, without, however, reaching a vertical 
line drawn in advance of the pupil. The eyes, which are situated on the right side, are large 
and sub-elliptical; their longitudinal diameter entering about three times in the length of the 
side of the head. The interocular space is very narrow and ridge-like. The head itself is con¬ 
tained about five times and a half in the total length of the fish. The branchial apertures are 
moderate, and not contiguous under the throat. 
The origin of the dorsal fin, which is bent towards the left side, takes place opposite the 
anterior rim of the upper orbit; it is quite elevated towards its posterior third, generally speak¬ 
ing well developed, and terminated at a short distance from the insertion of the caudal. The 
origin of the anal corresponds to a vertical line drawn posteriorly to the base of the pectorals, 
increasing in height towards its middle, and terminating evenly with the dorsal. The rays of 
both the dorsal and anal fins are rather stoutish, not bifurcated and provided on the left side 
with a membranous expansion which overlap each other when the fins are inclined backwards. 
The peduncle of the tail is very short and stright. The caudal fin, which constitutes a little 
less than the fourth of the total length, is rounded or convex upon its posterior margin. The 
insertion of the ventrals is placed in advance of the base of the pectorals ; they are broad and 
rather short, although extending beyond the anterior margin of the anal; their rays are not 
bifurcated. The pectorals are moderate sized, the left being somewhat smaller than the right, 
with a less decided bifurcation of its rays. 
Br. VI: VI; D 74 ; A 54; C 3, 1, 7, 6, 1, 4 ; V 6 ; P 1, 10. 
The body is covered with small scales, somewhat smaller on the left than on the right side ; 
they are sub-elliptical, longer than deep, and posteriorly entire and smooth instead of being 
pectinated. Over the opercular apparatus and head they are smaller also than on their respective 
side. Those occupying the base of the caudal are likewise diminutive and irregularly shaped. 
The lateral line, which is nearly straight, is slightly raised into a depressed curve immediately 
above the pectoral fins. 
The ground color of the right side is deep brown, maculated with blackish and yellowish ; the 
left side is of a uniform soiled yellow. 
The specimen described, the only one that has fallen under our investigations, measures seven 
and a half inches in total length. 
List of specimens. 
Catal. 
No. 
No. of 
spec. 
Age. 
Locality. 
When col¬ 
lected. 
Whence obtained. 
Nature of 
specimen. 
Collected by— 
697 
i 
Adult.. 
San Francisco, Cal_ 
1853 
Lieut. E. S. Williamson 
Alcoholic_ 
Dr. Heermann .. 
