CRABS 169 



And after a few weeks the form is changed once more, the skin thrown off, and 

 a perfect crab appears, about J of an inch long. A shell-less crab that is, one 

 which has " moulted " may often be found hiding in some crevice in a rock pool. 

 It is then quite soft to the touch, though the " shell " soon hardens. A crab 

 has to shed its skin frequently while growing, but as soon as it is mature, once a 

 year is sufficient. In so doing it loses even the coverings of its gills, its stomach, 

 eyes, antennae, jaws, and all its other parts. The eyes are on stalks, and are 

 like those of insects, compound, consisting of 3,000 or 4,000 square facets, and 

 thus enabling their owner to see in all directions without moving them. On the 

 head are two pairs of feelers. The lesser feelers have on each a small gland 

 containing salt and water these are the " ears " of the crab ; while on the first 

 joint of the greater feelers are similar glands by means of which it " smells." 



The Edible Crab (Cancer pagurus) is by far the most important of those in 

 the British seas. Small specimens may be found in rock pools, but the larger 

 ones can only be caught in deep water, by means of the well-known crab or 

 lobster pots baited with pieces of fish. This crab is brown in colour on the back, 

 possesses enormous claws, and is a tremendous fighter. An old specimen is 

 very often covered with barnacles and the tubes of some of the sea worms. 



The Common Shore Crab (GREEN CRAB, or HARBOUR CRAB) (Carcinus 

 mcBnas) is known to every seaside visitor. Its back is coloured protectively with 

 tints of yellowish green and brown, sometimes with black markings. It spends 

 a great part of its life out of water, possessing gills so made that they will 

 keep moist for a long time. 



The Velvet Fiddler (Portunus puber). This is one of the swimming crabs, 

 having its hindmost pair of legs flattened out into broad oval plates fringed 

 with hairs. Its name is given to it for the short, soft down like velvet covering 

 its blackish shell. The legs are striped with blue, with some scarlet on the 

 claws. 



The Slender Spider Crab (Stenorhynchus tenuirostris) has a very small, 

 triangular body, bright pink in colour, and long spider legs. Its carapace is 

 drawn out into a kind of beak. It is often found covered with seaweeds or 

 sponges. 



The Large Thorny Spider Crab (Maia squinadd), or " THORNBACK," has its 

 carapace covered with spikes, and frequently tufts of seaweed, which are planted 

 there by the crab itself as a sort of disguise. It is sometimes of considerable 

 size carapace 8 inches long, and legs 14 or 15 inches. 



The Common Swimming Crab (Portunus variegatus), common on Scottish 

 coasts, has the last pair of legs flattened into paddles. The swimming species 

 attack live fish, and are thus adapted for pursuing their prey. 



The Masked Crab (Corystes cassivelaunus) has, in the male, very long claws, 

 and is distinguished by the curious markings on the back, which resemble a 

 human face. The carapace is long and narrow, differing thus from that of all 

 other crabs. 



The Four-horned Spider Crab (Pisa tetraodori), the commonest of the spider 



