128 
SAGAETIAD^. 
shell. This process invariahly begins at the suture, and as 
it goes on the suture divides, the lateral portions separating 
more and more from each other hy shrinking ; thus reversing 
the steps by which the annular habit was assumed. 
So far as my own experience goes, the Adamsia always 
selects for its support the inner lip of a turbinate shell. 
Buccinum iindatuni I have generally seen chosen at Wey- 
mouth, but not rarely the various species of Trochus ; and 
a Helix I have already mentioned : xldams found it at 
]\Iilford Haven, on Murex despectus (= Fusus antiquus) : 
Thompson, at Belfast, on Bulla lignaria, as well as on the 
larger Troclii : E. Forbes, at the Isle of Man, on old Fusi 
and Trochi : Landsborough, at Arran, on Txirritella and 
Buccinum. Mr. D. Kobertson sends me specimens from 
Cumbrae, on Trochus umhilicatus. 
I believe that the shell chosen is always tenanted by a 
Hermit Crab, and that the species is invariably Pagurus 
Prideauxii. In this my observ'ation coincides with those 
of Dr. Coldstream, Thompson of Belfast, and Mr. D. Ro- 
bertson. Forbes seems to throw doubt on the constancy of 
this association ; having taken many specimens on the Manx 
coast, the shells of which were not tenanted by any crab. 
Similar examples have occurred to myself at Weymouth ; 
but when we remember how readily the Pagurus leaves its 
shell on alarm, and how terrifying the rough action of the 
dredge-iron must be, it seems the most obvious mode of 
accounting for the occasional vacancy of the shell, that it 
has been just deserted by its frightened tenant. 
The Adamsia itself in early life has the power of sliifting 
its quarters. Forbes observes that it “ seems to change its 
habitation according to its size : ” and I have liad two 
young specimens in my aquarium, which crawled sponta- 
neously from their shells, and attached themselves the one 
to a stone, the other to the frond of a sea-weed. While 
