146 
PLEUEONECTID M. 
THE FAMILY OF FLAT FISHES. 
A TOTAL want of uniformity between the sides of the head 
and also generaUy of the body. Eoth of the eyes are on one 
side of the head, whde the nostrils generally maintain their 
position m pairs on each side of the summit. The mouth is 
twisted, so that the two corners do not answer to each other 
and within the mouth there is generally a veil or cross mem- 
brane above and below. The body is much compressed; one 
side bearing colour, the other without it, and the structure of 
the skin differs in each. The abdominal cavity very short 
but the lobes of roe are contained for the most part in a 
recess which passes backward between the muscles towards 
e tail. Ihe vent close to or enclosed between the ventral 
fins which are near the throat. The fins nearly encircle the 
body, and the dorsal fin begins on the top of the head or in 
iront 01 it. 
In most if not all of these fishes the spinous processes of 
the vertebrie which support the rays of the dorsal fin, and are 
anterior to the pelvis, are turned forward for that purpose; 
while those of the vertebim on the same line of the back that 
are near the tail are directed backward. On the abdominal 
side all the spmous processes behind the abdomen itself are 
directed more or less backward. It is an essential part of the 
structure of these fishes that the superior and inferior processes 
of the vertebrse are very long, and those of the sides verv 
short; but m the Carter, and perhaps in others of this family 
which possess a lengthened form, while the superior and 
mferior processes ai-e comparatively shorter, the lateral processes 
are somewhat more developed. In the Topknot the spinous 
processes of the vertebrm are remarkably long, and anterior 
to the first of these processes there are numerous (what we 
