THE DECAPOD CRUSTACEA. 187 



used for carrying the eggs. The fourth, separated by a long 

 interval, is very much smaller. In the male there are three 

 unpaired appendages of small size. The unsymmetrical 

 condition of the abdominal appendages in Pagurus is a 

 point of much importance. 



We shall only mention here two species of Pagurus, the 

 common hermit, P. bernhardus, and the closely related P. 

 prideauxii of the West. "Bernard the Hermit" is recog- 

 nised by the fact that the great claws have their surface 

 covered with spinous tubercles and granules, and that the 

 terminal segment of the walking legs is twisted and 

 expanded. It is abundant everywhere. 



The P. prideauxii of the West Coast is very similar to 

 the common hermit, but the chelae are less tuberculated, 

 and the last joint of the walking legs is scarcely twisted, 

 not flattened, and grooved at each side. This form does not 

 occur on the East Coast, but is included here on account of 

 the interesting fact that it almost always bears the sea- 

 anemone Adamsia palliata on the back of its shell another 

 interesting case of commensalism in these hermits. In the 

 Clyde, and on other parts of the West and South, P. 

 prideauxii and its messmate are abundant. 



The other numerous British species of Pagurus mostly 

 live in deep water, or are confined to the South and West. 



The hermit-crabs possess so many obvious peculiarities 

 that they are quite unmistakable, but the next crab we shall 

 consider, though probably nearly related to the hermits, is 

 not infrequently erroneously described as a spider-crab. 

 This is Lithodes mala, the northern stone-crab, an animal 

 interesting alike in its distribution, its structure, and its 

 superficial resemblance to the true spider-crab Mala. As 

 the common name indicates, it is a northern species, one of 

 the few forms whose presence on the East Coast compensates 

 for the absence of the rich Mediterranean fauna of the 

 West and South. It attains a large size a span of twenty 

 inches, with a breadth of carapace of four inches, and 

 inhabits deep water. Though not a littoral form, it is, 

 however, included here because of its interest, and because 

 it may be not infrequently obtained from friendly fishermen, 

 and occasionally finds its way as a curiosity into fishmongers' 

 shops. Anyone accustomed to the Crustacea of the West 



