364 THE ZOOLOGIST. 
No. 4.—This crab is quite obscured by a very fine growth of 
sponge, Isodictya dichotoma, which rises and spreads from the 
carapace of the animal so as to completely shield it from view. 
Interspersed with this sponge there is a growth of the zoophyte, 
Plumularia faleata, the fronds of which are about two inches in 
length. Altogether this specimen is a fine example of protection 
obtained by resemblance to the ordinary rock-growth of the sea- 
bed, and it is only necessary for the crab to tuck in its legs 
and remain still to ata like the surrounding objects in its 
neighbourhood. 
No. 5.—This example consists of an irregular growth of a 
species of Isodictya, intermingled with some fine tufts of Sertularia 
argentea. In this specimen there is a pebble of limestone half an 
inch in diameter embedded in the sponge. 
No. 6.—This animal is a highly interesting specimen, owing 
to the number of parasitic growths which have secured a lodgment 
upon it. The whole of the upper carapace is covered with a 
dense mass of sponge, Halichondria panicea, which extends in an 
elongated branch for nearly an inch beyond the rostrum; its 
height is, however, only about half an inch. Over about two- 
thirds of the surface of this sponge is growing a second, Dysidea 
fragilis, its arenaceous net-work forming a beautiful object. At 
the termination of this mass there is a tuft of Sertularia argentea, 
and upon the right lateral margin of the carapace, immediately 
beneath the overhanging edges of the two sponges, is an 
Alcyonium digitatum, about half an inch long and three-eighths 
of an inch broad; beside this, again, is a tube of Serpula com- 
munis. Altogether it is a matter for surprise that an animal so 
obstructed and weighted is able to perform its ordinary life- 
functions, and it would certainly be a logical conclusion to arrive 
at, that Pisa Gibbsii is a species in the process of becoming 
extinct, notwithstanding its comparative immunity from attacks 
by fishes. 
(To be continued.) 
