180 LIFE BY THE SEASHORE. 



The other species, P. longicornis, though smaller, is much 

 more conspicuous and brighter in tint. It is found under 

 stones also, but not where there is mud, and usually in- 

 habits deeper water than its hairy congener. My best 

 specimens have been obtained from the roots of Laminaria, 

 either pulled out of the deeper pools, or cast on shore after 

 storms. The last constitutes a very important source of 

 supply for the smaller and rarer Crustacea. After many 

 an easterly gale the shore is strewn with giants from the 

 marine forests, and every plant has brought away with it 

 countless forms of animal life which once lodged in its 

 roots, stems, and fronds. 



Presuming, then, that you have obtained specimens of 

 both crabs, and that by a dexterous use of a camel's-hair 

 pencil you have removed a portion of the mud from the 

 hairs of P. platycheles, and so succeeded in revealing its 

 shape to some extent, we will consider the characters of 

 the genus. 



Both differ very markedly from Galathea in the shape 

 of the carapace, for it is almost circular and much depressed 

 in other words, truly crab-like. The abdomen is com- 

 pletely flexed, as in crabs in general, but it is large, retains 

 its seven distinct parts, and ends in a distinct, though 

 small and delicate, tail fin. You should not fail to notice 

 that, as in Galathea, the telson, or tail-piece, is curiously 

 marked, being composed of several pieces. As to the 

 appendages, the small antennules and the very long antennae 

 in essentials resemble those of Galathea. The third maxilli- 

 pedes are very interesting, because they present some general 

 resemblance to those of Galathea and the lobster; but yet 

 in the expansion of their basal joints they show an approach 

 to the shutter-like structure seen in the true crabs. As a 

 special peculiarity they exhibit a dense fringe of long hair 

 on the inner margin of their terminal joints. The structure 

 of the great claws differs in the two species, but in both 

 cases they are so modified by the hollowing out of the wrist 

 (carpopodite), that they can be held in a retracted position 

 (see Fig. 52). This is characteristic of the crabs as com- 

 pared with the long-tailed forms, which carry their chelipeds 

 outstretched. The next three pairs of appendages are walk- 

 ing legs, used for the support of the body. As in Galathea, 



