YOUNG STAGES OF ZEUGOPTERUS PUNCTATUS. 203 
eye had reached the dorsal edge of the head. The younger 
specimen was 11 mm. in length; the other, after being preserved 
and mounted, is 10 mm., a diminution which may be due to the 
process of preservation, or partly perhaps to the advance in meta- 
morphosis, a reduction of size during the transformation having been 
observed by me in the flounder. 
A sinistral Pleuronectid having these periotic spines was described 
and figured by McIntosh and Prince (Trans. Roy. Soc. Edinb., vol. 
xxxv, pl. ui, 1890, p. 846) as a stage in the history of the turbot. 
The specimen was 9°8 mm. long, and another specimen a few mm. 
longer, having similar spines, is mentioned. The mention of the 
spines alone seems to indicate that these specimens were either of 
the same species as the specimens obtained by me, or a closely allied 
form. The figure given, probably drawn from a spirit specimen, is 
not perfectly characteristic. 
A discussion of the identification of the larva with otocystic spines 
is given by Prof. McIntosh in the Tenth Report of the Fishery 
Board for Scotland, p. 279. He refers to Mr. Holt’s opinion, that 
it belongs to the brill, and mentions another specimen, taken on 
Smith Bank off Caithness, in which the dorsal had 87 and the anal 
62 rays. 
In the Eleventh Report, published in 1893, Prof. McIntosh makes 
a further contribution to the question of larval sinistral Pleuronectids. 
He mentions no new specimens of the form here under consideration, 
but gives his reasons for concluding that the young specimens shown 
in pl. xiv, figs. 7, 10, and 11 of the Tenth Report, belong to Zeugop- 
terus punctatus : these were 4°5 to 9 mm, in length. He also thinks 
it possible that the form with periotic spmes may be a later stage 
of the same species, the diminution in the size of the eye being due 
to changes accompanying growth, or to abnormality. With this 
opinion-I cannot agree. The form without the spines has larger 
eyes, and has the eye on the edge of the head when only 9°5 mm. 
long ; it is, I think, a distinct species. 
It is somewhat difficult to follow the successive discussions in 
which Prof. McIntosh has described and compared his specimens of 
young sinistral forms, more particularly as his figures are, as a rule, 
inadequately characteristic, often having been delineated from dead 
and imperfectly preserved specimens. Mr. Holt has been able to 
give a more comprehensive and more completely illustrated descrip- 
tion of specimens of similar characters procured in the survey of the 
west coast of Ireland in 1890 and 1891. His results were published 
last year in the Scientific Transactions of the Royal Dublin Society, 
vol. v, ser. 83. The form with periotic spines (if it is a single 
species and not more than one) is represented in Mr. Holt’s collection 
