382 CRUSTACEA. 



The connexion of the two species is surely more than accidental. It 

 may be further stated, that in the localities whence P. Pridemixii was 

 obtained P. Bcruhardus is very common ; and in the loughs mentioned a 

 few individuals of two or three other sjjecies of Paguri have been pro- 

 cured. 



I had observed the occurrence of the Pagunis in Trochi [ T. cinereus, 

 &c.], and Bulla lignaria : — to these may now be added Buccinum unda- 

 tum and Nutica Aldori. The smaller shells thus I'esorted 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 fi'om 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 Kothsay and Kames 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 Par/urus 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- 

 panionshi]) is not invariably constant. By Dug^s 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 occun-ed. I have often found them tenanted instead by 

 Paf/urns Bernliardus. 



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 Alci/oniuni cchinatum (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 Alcyoniiini 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. Doivn, Oct. 2nd, 1851. I found the remains of a full- 

 grown one in the stomach of a cod-fish taken off here. 



Oct. \{)th. 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. Bcrnhardus 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. V. 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 copied in John- 

 ston's British Zoophytes, p. 219. 



t Mr. J. V. Thompson's collection is now in the Royal Dublin Society's 

 Museum. 



