120 Memoirs of the Indian Museum. [Vol. II, 



outer spines, which are unusuall}^ 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 s err ata 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 externally. 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 carina 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 only 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 



