INTRODUCTION. 13 



of the bottom. It is, perhaps, at this period of repose that 

 the crops of seaweeds and corallines fix themselves, as they 

 are often seen beautifully adorning them ; shells of different 

 species, but especially Oysters and Mussels, are also found 

 adhering, and on the smaller kinds, as of lnachus and Pisa, 

 sponge will grow so luxuriantly as to conceal the whole ca- 

 rapace, with tufts on the legs to the extremities." 



These long-legged Crabs are frequently covered with sea- 

 weeds, sponges, and other marine productions, which so com- 

 pletely change their appearance as to render them no longer 

 recognizable. In this way Macropodia occidentalis (Guil- 

 ding, Linn. Trans, xiv. 335) disfigures itself in the West 

 Indian Seas, and watches for its prey. The British Spider 

 Crabs [lnachus and Arctqpsis) are often completely covered 

 with masses of algse, the roots of which take a secure hold 

 amongst the hairs that clothe the carapace and limbs (Bell's 

 Brit. Crust, p. 24). Say and Le Sueur fancied that these 

 marine productions were merely entangled mechanically,* 

 but there can be no doubt that they grow and flourish on 

 their strange locality. 



Professor Bell has watched the Arctopsis (Pisa) tetraodon 

 waiting for its prey. He remarks that the Crabs of this 



* Joura. Acad. Sc. Phil. vol. i. p. 80. 



