THE CRUSTACEA 163 



for protection, but Portunus trusts to his weapons, and his 

 skill in their use. 



Closely allied, but of smaller size, and less velvety, the 

 shell finely sculptured with waved lines, and of uniform 

 red colour, is Portunus conugatus. 



Portunus depurator and Portunus Tiolsatus resemble these, 

 but are of rather smaller size than the last, and are not of 

 striking colours, being simply of a yellowish brown. 



Portunus marmoreus is a beautiful representative of this 

 genus. It is about as large as the last that is, about two 

 and a half inches across the back. It is on the same lines 

 of structure, but is of a cream-colour, with a marbling of 

 light purple. It is rather rare. 



Portunus arctuatus, about an inch across, is told at a 

 glance, by its having the front of the carapace, the part 

 between the eyes, in smooth arched form ; the others are 

 in several angles, and spined. Its colour is yellowish, with 

 a black and white chequering on the first ring of the ab- 

 domen. 



Portunus pusillus, the pigmy of the race, is about three- 

 quarters of an inch across. Its colour is reddish brown. 

 The two first named of this genus are found, the first 

 commonly, the latter rarely, under stones in rocky places. 

 All the others frequent open ground in shell-gravel bottom, 

 and bury just beneath the surface for concealment. 



Allied to this genus is Portumnus variegatus. This one is 

 of different outline, being a little longer than broad. It is 

 about an inch across. The colour is yellowish white, some- 

 times pure white, finely speckled with black. It frequents 

 sandy shores, and is not common. 



Last of the swimming crabs, and in fact the only one that 

 does swim, in the sense of leaving ground and travelling 

 any distance through water, is Polybius Henslowii (Fig. 70). 

 This is a beautiful form, with a circular carapace, very flat 

 and smooth, about two inches in diameter. 



