IpUis scptunspinosa. 



Ixa cylindrus. 



Nursia plicdta. 



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

 structures 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 represented 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. 



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 coasts 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 

 antennse, sp 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 within reach, 

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

 and formidable hands. 



