YY 
S12 SPOLIA ZEYLANICA. 
wet sand. I watched one do this, waited for a few minutes, 
and then dug down at the spot and found that the crab and 
the air chamber had disappeared quite deep into the sand. 
Presumably, although it is impossible to see this part of the 
process when the chamber is completely roofed in, the crab goes 
on working in the same way until the air bubble or chamber is 
carried down to the requisite depth, so that the tide overhead 
will not disturbit. In this air chamber the crab remains until 
the tide has gone down and he can come up again to feed. 

Fic. 3.—Section showing stages in the formation 
of an air chamber by Dotilla. 
The habits of a nearly-allied species of crab is described 
by R. P. Cowles,* who has observed the habits of Mycteris 
longicarpus, Latreille, in the Philippine Islands. But though 
he gives photographs of the sand pellets and describes the 
corkscrew descent of the hiding crab, with a plate illustrating 
the crab in the air chamber, he appears to think that the 
pellets are thrown up and the air chamber is made by the 
rapidly-descending crab. As I have recorded above, these 
two habits are quite distinct. The air-chamber method is 
used by those which live on the wet sand and have no per- 
manent burrows. In one case I noticed that one of the crabs 
living on the dry sand most carefully closed up the entrance 
to his burrow with several lumps of sand, presumably to 
retain the air inside when the tide came up. 

* R. P. Cowles: ‘‘ Habits of some Tropical Crustacea,’ II. Philip- 
pine Journal of Science, Vol. X., Sec. D, No. 1, p. 11. 
