120 
Memoirs of the Indian Museum. 
[Voi.. II, 
outer spines, which are uiiusuall}^ stout, and the inner ones ; these latter also very 
stout, numbering about six, arranged in a double row with fine hairs interspersed. 
Exceptionally large specimens have a capitulum about 4 mm. long, but it is more 
commonly from 2 to 3 mm. long even in individuals bearing eggs. A common species 
on Scylla serrata in Indian estuaries. 
Gruvel separates his Dichelaspis maindroni from D. cor on the following charac- 
ters (i) difference in shape of the upper part of the capitulum, (2) absence of any 
trace of the terga, (3) absence of lines on the external surface of the capitulum, (4) 
small differences in the cirri, mouth parts and anal appendages. The first of these is 
not only a variable character but one peculiarly liable to be obscured by different 
methods of preservation ; the second is a character not constant either in this species 
or in others allied to it ; the same remark applies to the third, while those included 
under the fourth heading are discussed so briefly by Aurivillius in his original descrip- 
tion of D. cor that it is not possible to make a detailed comparison. I can only say 
that I have found the cirri, etc., extremely variable even among individuals resem- 
bling one another externall3^ The parallel lines on the external surface of the capi- 
tulum in some individuals clearly represent the outlines of the original five valves, in 
others they are confined to the upper part of the capitulum, in others the^'- can just 
be traced at a few points, while in others they are quite absent. 
Gruvel distinguished three varieties, which, for very sound reasons, he refused to 
recognize as distinct species. They are characterized as follows : — 
Var. A has the extremity of the basal branch of the scutum truncate and 
expanded and the occludent branch considerably broader in the middle 
than at the base. The extremity of the basal branch of the cariiia is also 
expanded and truncate. 
Var. B has the same features to a less strongly marked extent, except that the 
occludent branch of the scutum is barely broader in the middle than at the 
base. 
Var. C has all the valves linear, without expansions at the extremity, of any. 
The three varieties occur in the Bay of Bengal, but var. A is commoner than 
the others and is often the onl>^ one found on the gills of a crab, although the three, 
with intermediate stages, sometimes occur together. The degree to which chitinous 
points are developed on the external surface of the capitulum and peduncle is very 
variable. 
By the kindness of Professor Bouvier I have been able to examine co-types of 
Gruvel’s three varieties. Too much stress must not be laid on the differences between 
them, for many intermediate forms occur. Also by the kindness of the same zoologist, 
I have received co-types of Gruvel ’s D. coutierei, which I had long suspected to be a 
variety of D. maindroni founded on specimens in which the penis was not fully devel- 
oped. An examination of the co- types confirms me in this view, for they all appear 
to be immature The parallel and transverse chitinous bars on the capitulum are not 
so conspicuous in any of the specimens I have seen as they appear to be in Gruvel’ s 
