246 THE ZOOLOGIST, 



Spider-Crab differs, in my experience, according to whether the 

 animal is alarmed whilst standing in an exposed situation, or 

 whether it is alarmed in one of its favourite positions, wedged 

 into a hole or clinging closely to the under surface of a pro- 

 jecting piece of rock. If a Pisa tetraodon be touched with a 

 rod when in the former position, it at once presses its body 

 as closely as possible to the ground, and then begins to 

 sidle away as quickly as caution permits. If, however, it is 

 in one of the latter positions, it does not usually seek safety 

 in flight, but presses its body tightly against the rock and 

 remains perfectly still, resisting with all its strength any attempt 

 to move it from side to side or to pull it away from the rock. 

 Its behaviour in this respect, as I have frequently satisfied 

 myself by experiment, is. the same whether its body carries a 

 disguising mass of seaweeds or not. A Four-horned Spider-Crab 

 may often be seen clinging to the under surface of a jutting piece 

 of rock which would appear to be far too smooth to enable it to 

 obtain a hold, but the comb-like row of spines on the inner 

 margin, and the sharp-pointed tip, of the terminal joint of each 

 of the eight walking legs, enable the animal to obtain a good 

 and very ready grasp. One Spider-Crab hung (for at least a 

 day, I believe) after death to the under surface of such a jutting 

 rock, and it was found that some of the rows of spines had been 

 introduced before death so cunningly into holes and depressions 

 that each leg required to be detached with some care. Carrington 

 and Lovett mention the " very secure " hold of this Spider- 

 Crab, remarking that the sharp end joint can be clenched back 

 upon the next one,* but they do not mention the use of the 

 spines. The sharp point of the end joint and the spines (which 

 are shown in fig. 2) are especially useful when the animal 

 attempts a characteristic method of escaping from an enemy, or 

 from the annoyance of being touched with a rod. If the Spider- 

 Crab is exposed on the rocks when so attacked, it sidles away in 

 the manner described above, but immediately it reaches the edge 

 of the rock it deliberately turns over the edge, and, once beneath, 

 remains perfectly still, clinging upside down. 



The attitude assumed by a Four-horned Spider-Crab when at 



* J. T. Carrington and E. Lovett, "Notes and Observations on British 

 Stalked-eyed Crustacea," ' The Zoologist,' vol. xxxix, 1881, p. 359. 



