284 Mr. W. Thompson on the Crustacea of Ireland. 



lough." It is commonly found in Modiolus vulgaris on the Irish 

 coast, where it is of much more frequent occurrence than in the lo- 

 cality in which Dr. Leach endeavoured to ascertain the number found 

 in a certain quantity of mussels. In the article Crustaceology (Edin. 

 Ency.) it is remarked that — " in one hundred of Mytilus modiolus, 

 Dr. Leach found three of this species." On opening eighteen spe- 

 cimens of the Modiolus vulgaris of various size — the produce of 

 dredging off Bangor (co. Down) in October 1835 — I found fourteen 

 individuals of P. pisum, all females : in one shell only two of the 

 crabs occurred. I have subsequently opened quantities of these Mo- 

 dioli with similar results as to the number of the Pinnotheres, but in 

 all other instances more crabs were obtained from a like number of 

 shells in consequence of more of the Modioli producing two of them. 

 The smallest Pinnotheres I have seen was found by Mr. Hyndman 

 in a living Cardium exiguum dredged by us in Strangford lough in 

 Oct. 1834. It is a male: the carapace is under a line in length; 

 the entire breadth of the crab from the extremities of the out- 

 stretched legs is 3 lines*. The Cardium is under 3 lines in length, 

 and barely exceeds that admeasurement in breadth, so that the crab 

 when in the position just mentioned must have on both sides touched 

 the walls of its chosen prison. The Pinnotheres likewise inhabits the 

 Cardium edule. Before me is one of these crabs, of which the cara- 

 pace is 2 lines in breadth, obtained by Mr. Hyndman in a full-grown 

 C. edule from Strangford lough ; but from the Sligo coast, where this 

 shell attains an extraordinary large size, a crab with a carapace 4 

 lines in breadth, and with outstretched legs 7 lines across, was once 

 kindly brought to me by LordEnniskillen. Mr. R. Ball informs me that 

 on two occasions he obtained a great number of the Pinnotheres, and 

 which were all males, from the Cardium edule taken at Youghalf — 

 about nine out of every ten cockles contained a crab. On opening 

 oysters from Tenby, in Wales, he has likewise procured the Pinno- 

 theres. This crab, like the Pagurus, occupies different species of 

 shells according to its size, and at every age generally selects such 

 as with outstretched legs it would fill from side to side — this of 



mens before me as I write, have all the anterior part of the shell produced 

 as in P. Latreillii and P. varians of Leach (pi. 14.), and consequently un- 

 like the two-lobed anterior part of P. Montagui and P. veterum of the same 

 author. All of my specimens but one have the large hands of P. varians — 

 the exception has them no larger than in P. Latreillii : surely this species, 

 as represented by Leach, is a male — M. Edwards notes it as a j r oung female. 



* In the ' Entomological Magazine,' vol. iii., the Zoea of this Pinnotheres 

 is described and figured by Mr. J. V. Thompson. 



f With respect to another part of the coast of Cork, Mr. J. V. Thompson 

 observes — " Let any person take a sweep with a dredge on any bank of old 

 mussels, modioli or pinnee, where the Pinnotheres have been before observed, 

 and almost every shell will be found to contain one full-grown female, some 

 two, and others three, independent of young ones and males, which occa- 

 sionally occur in common with the females. * * * As the fishermen at Cove 

 often have recourse to those shell-fish for bait, I have had a pint and upwards 

 of the pea-crab brought to me out of the mussels obtained in a few hauls of 

 the dredge."— Ent. Mag. vol. iii. p. 86. 



