596 



THE MASK-CRAB. 



IN the course of the preceding pages we have seen many instances of curious struct- 

 ures which seem to be wholly supplementary and of no use whatever to the creature. 

 The very fact of their existence is a proof that there is some use for them, although 

 their office is so obscure as to elude all present researches. Such an example is 

 given in the present illustration, of which it occupies the uppermost place, and is rep- 

 resented as climbing over a large flat stone. On each side of the body is a large 

 cylindrical projection, so that the extreme measurement from side to side is nearly 

 equal to three times the length of the body ; the claws are long and feeble, all the 

 force seeming to be thrown into the two projections. This crab is a native of several 

 parts of Asia, and is found both in India and off the Philippines. 



On the right hand of the illustration is seen another odd-looking crab, having its 

 carapace scooped and grooved in a wonderful manner. This is an example of the 

 genus Nursia, and is here given in order to show the strange variety of form which is 

 assumed by the carapace. It is found in the Indian Ocean. 



Iphis septemsplnosa. 



Ixa cyliadrus. 



Nursia pHctta. 



The last figure in the illustration represents the SEVEN-SPINED CRAB, so called on 

 account of the seven sharp points that project from the carapace. There are several 

 large species of this genus, one of which has nine spines instead of seven. In this 

 curious creature the arms are longer and more slender than in the preceding species, 

 and the claws at their extremities are exceedingly delicate and feeble. This crab is 

 a native of the Eastern seas, and is generally captured off the coast of India. 



THE two larger figures in the next illustration represent the same species in two 

 different attitudes, that on the left being intended to show its general aspect, and 

 that on the right being given for the purpose of exhibiting the position which it 

 assumes while watching for prey. 



As will be seen by reference to the engraving, the MASK-CRAB buries itself in the 

 sand or muddy bed of the sea, and only permits its snout to project, with the long 

 antennae, so as to feel (or, as some suppose, to listen) for approaching prey, and the 

 eyes to look in all directions for any eatable creature that may haplessly wander with- 

 in reach, and the claws, in order to seize the prey when it passes within the grasp of 

 their long and formidable hands. 



