286 THE SEA SHORE 



of the crab, except, perhaps, a very small linear portion between 

 the bases of the last pair of legs, where the first part of the 

 segmented abdomen is visible from above. 



The true crabs of our seas may be divided into four groups, as 

 follow : 



1. Oxystomata, or Pointed-mouthed Crabs ; 

 '2. Oxyrhyncha, or Pointed-beaked Crabs ; 



3. Catometopa, with forehead turned downwards ; and 



4. Cyclometopa, or Bound-headed Crabs ; 



and we shall briefly observe some of the more conspicuous and 

 interesting species in the order of the tribes as just given. 



The first division is not well represented in our seas, the 

 principal species being the Nut Crabs and the Long-armed Crab, 

 all of which may be distinguished by the peculiar arrangement 

 of the foot-jaws, which, when closed, form a triangle with an 

 acute angle turned towards the front. The Nut Crabs are mostly 

 small ; and, since they generally inhabit deep water, are not 

 commonly seen on the shore ; but perfect specimens may some- 

 times be found among the contents of fishes' stomachs. They 

 derive their name from the nature of the carapace, which is of a 

 rounded form and very hard and strong. 



Pennant's Long-armed Crab (Corystes Cassivelaunus) may 

 commonly be seen entangled among fishermen's nets, but is not 

 often seen on the shore at low tide. Its carapace is very convex 

 above, with three sharp spines on each side, and the grooves are 

 so arranged as to suggest the appearance of a face. Our illustra- 

 tion represents the female, but the ' arms ' of the male are very 

 much longer than those of this sex. 



The Sharp-beaked Crabs (Oxyrhyncha) include all those long- 

 legged creatures that are known collectively as the Spider Crabs ; 

 and here, again, we have to do with species that almost exclusively 

 inhabit deep water. Although this is the case, but little difficulty 

 is experienced, as a rule, in obtaining specimens. If you are 

 unable to take a trip in a trawler for the purpose of examining the 

 ' rubbish ' that is dredged from deep water, simply obtain permission 

 to search the nets and the boats as they arrive in port. In the 

 latter case you are almost certain to find the crabs you require, 

 though it is probable that some of the species will have been 

 damaged by the hauling and shaking of the nets. 



These interesting crabs have been spoken of as the monkeys 



