On the Development of the Pleuronectidce. 219 
Donovan is said to have mistaken one of these abnormally 
developed specimens for a new species, and to have called 
it Plenronectes cyclops. 
In the summer of 1863, I myself obtained, in dredging 
over a sandy bottom in the Firth of Forth, three young 
Pleuronectidse, each about half an inch long, and ap- 
parently belonging to the genus Platessa. In all but one, 
the eyes and dorsal fin were conformed exactly as in an 
adult flounder, but the remaining one, which I have the 
pleasure of exhibiting to the Society to-night, has one eye 
on the middle line of the top of the head, with, as in M. 
Van Beneden's specimen, the dorsal fin stopping short 
behind it. 
As regards the imperfectly developed or monstrous flat 
fishes already referred to, I am enabled to exhibit to you to- 
night a specimen of a turbot presenting the peculiar con- 
dition of the eyes and cephalic extremity of the dorsal fin 
characteristic of those specimens. Through the kindness of 
Professor Goodsir, I have also had an opportunity of dissect- 
ing a similarly malformed flounder {Platessa flesus). 
These malformations are flat fishes in which the turning 
round of the upper eye to the other side of the head has 
been arrested when it has got about the middle line of the 
top of the head ; and in consequence the passage forwards, 
and tying down of the anterior part of the dorsal fin, has also 
been stopped, or obviously it would cross over the eye in- 
stead of passing by the side of it, as it ought to do. It 
accordingly projects upwards and forwards in a free pointed 
process, overhanging the eyes, as may be seen in the speci- 
men on the table. It is worthy of remark that all these ab- 
normal specimens are equally coloured on both sides, as if the 
animal, not having perfectly acquired the characteristics of a 
flat fish, swam with either of its sides upwards at pleasure, or 
it might be that it swam, not on its side, but with its mesial 
plane vertical, as in an ordinary fish. In the specimen on 
the table, it will also be observed that not only are both sides 
coloured, but that the rough bony tubercles, usually charac- 
teristic only of the ocular side of the turbot, are here also 
equally abundantly distributed on the opposite one. 
VOL. III. 2 F 
