SOME COMMENSALS OF INDIAN ALCYONAltlANS. 
93.) 
D. dorsipes and D, facc.hino (Fig. 2). Both love sandy bottom, and Dorippe dor- 
sipes is particularly numerous at Madras ; numbers are often to be found in 
the rubbish tlnown aside from fisheimen’s nets. Their usual habit here is to 
carry over their back a vah'e of some species of thin bivalve shell, concave side 
down, of size suitable for effective concealment. The illustration given (Fig. 5) 
shows the usual appearance of this crab when carrying his buckler in position, 
held securely by the claws of the two last pairs of legs ; the points of these claws 
show over the edge on both the fore and hinder margins of the shell. In many 
cases, the defence is increased by the presence on the surface of the shell of a 
little pale-colouroi anemone. .lust as the association of Spnapla striata with the 
spider-crab already noted, gives added j)rotection because of the burr-like spi- 
cules in the skin of the synapta, so here the crab, perching an anemone upon 
the concealing shell, provides himself with a whole series of ready-made batteries 
of stinging cells, capable of frightening away any small fishes that might otherwise 
penetrate the disguise of the concealing shell. Hermit-crabs are known to 
transfer the anemone Adamsia from other gastropod shells to those which they 
use for their own habitation, so here it seems certain that Dorippe has a 
related habit, but whether it merely selects a shell on which an anemone 
already is settled, or whether it actually detaches the anemone from its first 
foothold and then transfers it to the shell which it has already selected for its 
concealing cloak is not known. This is one of those interesting points that 
can only be settled by keej ing these animals under close observation in am 
Aq uarium 
Fig. 6. — Lumhrvs, a crab that lives o i shingly bottc m ; the carapace in this 
case is concealed by a mask of oyster shells and barnacles. 
(Original). 
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