Memoirs of the Indian Museum. 
TOO 
[Vox.. II, 
species or of D. neptuni from the genus Dichelaspis. D. neptuni is closely related to 
D. sinuata , of which it may be a local race or even a chance variety. 
Hoek, in his recent account of the Pedunculate Cirripedes of the “ Siboga,” 
divides the genus into seven sections, much on the same principles as those adopted 
in my key, which will serve to distinguish the Indian species not only from one 
another but from most other forms. There are, however, a few points that I have 
been obliged to leave in doubt when preparing it. They may be noted here. I put 
them in the form of questions as follows : — 
(1) Is D. sinuata merely a local race of D. lowei, Darwin ? Except as regards 
size (which is not a reliable specific character in the genus owing to the 
fact that few individuals reach the maximum dimensions they appear to 
be capable of attaining) the difference between these two forms lies 
mainly in outline, and this is not only a variable character in the softer 
Lepadidæ, but also one liable to be altered by bad or prolonged preserva- 
tion. 
(2) Is D. sinuata distinct from the Japanese D.aymojiini, Tesson ? So far as 
external characters go, I have examined intermediate specimens. 
(3) Is D. millleri, Coker, distinct from D. lowei ? The two are certainly verj?- 
similar, but I have not seen either. 
(4) Are Stebbing’s D. hoeki and D. antiquce distinct from one another ? The 
external differences between them are certainly smaller than those which 
separate the extreme forms of D. tridens, a species belonging to the same 
section of the genus. 
The following table shows the geographical distribution, bathymetrical range and 
hosts of the Indian species of Dichelaspis , so far as these elements in their biology 
have been ascertained. It will be noted that all the species are parasitic, or at least 
commensal, in habits, but that the degree to which they are so varies considerably, 
some attaching themselves to the exterior of their host, others penetrating within its 
gill-chamber. 
An examination of the table shows that, with one exception, the Indian representa- 
tives of the genus habitually affix themselves on settling down in life to the body of 
some hard-shelled crustacean. The one exception is D. grayii which, so far, has always 
been found on the skin of sea-snakes. x\s regards the species of Dichelaspis commonly 
found on Crustacea it will be seen that at least two have been found occasionally on the 
shells of echinoids, and that one (D. warwickii) sometimes fixes itself to the shells of 
living molluscs, to the skin of sea-snakes and even to that of fish. As regards the crus- 
tacean hosts of the genus, there is abundant evidence that the majority of the bar- 
nacles prefer a hard-shelled decapod but are not particular as to its family. Decapods 
are of course by far the commonest crustaceans of a considerable size and with hard 
shells ; it is noteworthy that I have not found a single barnacle of any genus attached 
to the carapace, limbs or gills of any of the soft-shelled prawns dredged by the “ Investi- 
gator ” or purchased in the Indian markets. Probably these decapods cast their skin 
