ii6 
Memoirs of the Indian Museum. 
[VOL. II, 
Dichelaspis grayii is common on the sea-snakes of Indian seas and I have been 
able to examine over 800 specimens in all. This series exhibits every gradation 
between the typical form and D. pcllucida^ of which Darwin said, “ I should not be 
much surprised if the present form were to turn out to be a mere variety ” [of D. 
grayii\ 
The variety described above as var. pernuda is, however, a most remarkable 
form. I have found it in considerable numbers on three sea-snakes from different 
localities, always by itself so far as other cirripedes were concerned. A careful 
comparison of cirri, mouth parts, etc., with those of specimens of the typical form 
of the species shows no constant difference, while Darwin’s description of these 
organs fits more exactly to one specimen of the variety than to any individual of the 
typical form I have dissected. The long anal appendages, which in some specimens 
of the typical form are distinctly segmented, are particularly characteristic of the 
Fig. g. — Mandible and maxilla of D. grayii var. pernuda, x 240. 
species, although their exact relative length is variable, while the arrangement of the 
armature and ornamentation of the mouth parts also affords a sufficient means of 
diagnosis. 
The new variety affords another link between three subfamilies of the Lepadidæ 
{i.e., the Tepadinæ, the Pœcilasmatinæ and the Alepadinæ). The nakedness of the 
capitulum and its lack of a muscular layer may be only an adaptive resemblance to 
the genus Alepas, from which the well-developed cirri at once distinguish it. The 
absence of a muscular layer and of lateral appendages separates it from Heter alepas, 
to which, however, it exhibits a certain resemblance as regards the anal appendages 
and mouth parts. Both the variety and the typical form of the .species, moreover, 
differ as regards these structures from most other species of Dichelaspis ; but it is 
impossible to separate them from that genus. 
