84 INTRODUCTION TO ZOOLOGY. 



of the North of Ireland, nor, as far as we know, is it ever 

 employed there as an article of food. Mr. R. Ball states,* 

 that when these Crahs are about to change their shells, or have 

 recently done so, they are sought for under the sea-weeds, at 

 low tide, by the fishermen at Youghal, chieily as bait for 

 flat-fish. In this soft state they are called Pilcrabs. From 

 their habits of elevating their claws in a threatening attitude, 

 when molested, they have, on the coast of Normandy, the 

 name of "Crabes enrages." 



i The Pea-crabs form an interesting group, from their dimi- 

 nutive size, and their singular habitation in bivalve shells, one 

 of which was celebrated in connexion with the Crab; as, 



"The anchored Pinna and her cancer friend." 



The Pinna, according to tradition, being warned of the ap- 

 proach of danger by the alacrity of the little Crab, who was 

 the joint and friendly occupant of her mansion. One species 

 (Pinnotheres pisum) is so common on our Irish coast, that 

 Mr. W. Thompson obtained fourteen of them, by opening 

 eighteen of the large or "Horse-mussel," dredged off the 

 County Down shore; and in the common Cockle at Youghal, 

 Mr. Ball found them so abundantly, that about nine out of 

 every ten Cockles contained a Crab. Two and even three 

 Crabs are occasionally found in one Mussel, or one Pinna. 

 The Hermit-crabs belong to a different order. The tail is 

 prolonged and soft, being destitute of the hard calcareous 

 covering which protects the anterior portion of the body; and 

 hence, in self-defence, the animal is obliged to occupy some 

 univalve shell, which has been deserted by its original occu- 

 pant. From the fact of each Crab being thus the solitary 

 inmate of its retreat, the common English name has no doubt 

 been bestowed. The species most abundant on our coast 

 (Pagurus Bernhardus) is found in shells of very different 

 dimensions, and from time to time leaves its abode, as it feels 

 a necessity for a more commodious dwelling. It is said to 

 present on such occasions an amusing spectacle, as it inserts 

 the tail successively into several empty shells, until one is 

 found to fit.f We learn from Professor Bell, however, that 



* In Mr. W. Thompson's Paper, 

 t Carpenter's Zoology, page 252, 



