382 
CRUSTACEA. 
The connexion of the two species is surely more than accidental. It 
may be further stated, that in the localities whence P. Prideauxii was 
obtained P. Bernhardus is very common ; and in the loughs mentioned a 
few individuals of two or three other species of Paguri have been pro- 
cured. 
I had observed the occurrence of the Pagurus in Troclii [ T. cinereus , 
&c.], and Bulla lignaria : — to these may now be added Buccinum unda- 
tum and Natica Alderi. The smaller shells thus resorted to, as the last- 
named, and Trochus cinereus, may be said to have merely formed the apex 
of the tenement, as “ the thin horny expansion attached to the aperture of 
the shells, and forming as it were an extension of the body- whorl in a 
spiral form,” * constituted from one-half to two-thirds of the entire habit- 
ation of the crab. 
Dr. Coldstream, in treating of the Actinia maculata obtained by him 
at “Torbay, and in Rothsay and Karnes Bays in Bute,” remarks, that the 
shell which it covered was “ always found inhabited by a variety of the 
hermit-crab.” The “ variety ” thus alluded to was probably P. Prideauxii. 
By Dr. Coldstream, and also by myself, the Actinia and Pagurus under 
consideration have always been found associated. Dr. Leach makes no 
mention of their connexion ; and Prof. Forbes states that not a single 
specimen of the Actinia taken in the course of a season by him about the 
Isle of Man “ had either hermit-crab or horny disc.” (Annals, vol. v. p. 
183.) It would thus appear, that on the British coasts this strange com- 
panionship is not invariably constant. By Duges the two species have 
been found associated on the coast of France. 
Dr. Coldstream enters pretty fully into the subject of the “ horny ex- 
pansion,” and, after speculating upon its formation, thinks that it is proba- 
bly “ produced by the Actinia.” Opposed to this view, however, is the 
fact, that shells possessing the horny expansion are frequently dredged in 
localities where the Actinia was never met with — and where the P. Pri- 
deauxii never occurred. I have often found them tenanted instead by 
Pagurus Bernhardus. 
On examining such shells with horny expansions as are preserved in my 
cabinet, I find the expansions to consist simply of a development or con- 
tinuation of the Alcyonium echinatum (and which it occurred to Dr. Cold- 
stream might be the case) beyond the shell itself after this is covered, or 
nearly so, by the zoophyte. May not this Alcyonium be selected by the 
Actinia as a base upon which to fix itself, on account of its papillary 
eminences, thereby enabling it — the parasite — to retain a firmer hold or 
“ seat ” ? 
Newcastle, Co. Down, Oct. 2nd, 1851. I found the remains of a full- 
grown one in the stomach of a cod-fish taken off here. 
Oct. 10th. There have been severe gales of late. On the beach, North 
of Newcastle, I found three or four adult specimens to-day, all freed from 
shells ; more than I ever saw of P. Bernhardus here in a day, i. e. on the 
beach three Irish miles in extent, walked back and forward by different 
tracks. 
P. erinaceus, J. V. Thomp.f 
In the collection of Mr. J. Y. Thompson is an Irish specimen of a 
Pagurus considered as undescribed, and so named by him. 
* Dr. Coldstream in Edin. New Phil. Journ., vol. ix., and cojpied in John- 
ston’s British Zoophytes, p. 219. 
f Mr. J. V. Thompson’s collection is now in the Royal Dublin Society’s 
Museum. 
