VI 



PAGURIDEA SYMMETRICAL IIERMIT-C R.M'.S 



1/3 



Besides the ordinary twisted Tagurids which iiiliabit Ga>- 

 teropod shells, there are a few which preserve the symmetry of 

 the body. The interesting Pylocheles miersii 1 (Fig. 118), 

 taken by the Investigator in the Andaman Sea at 185 fathoms. 

 inhabits pieces of bamboo; it is perfectly symmetrical, wiih 

 well -developed pleopods and 

 symmetrical chelae, which, 

 when the animal is withdrawn, 

 completely shut up the entrance 

 to its house (Fig. 118, A). 



It is doubtful whether this 

 animal ever inhabited a spiral 

 shell or not in its past history ; 

 but there is no doubt that 

 a number of peculiar crabs, 

 which caused the older sys- 

 tematists much trouble, are 

 Pagurids, derived from asym- 

 metrical shell - haunting an- 



ccstors that have secondarily 

 taken to a different mode of 

 life, and lost, or partially lost 

 those characteristics of ordinary 

 Hermit-crabs which are asso- 

 ciated with life in a spiral shell. 

 These are the Lithodidae and 

 the " Kobber - crab," Hiryus 

 latro, of tropical coral islands. 



Although the Robber-crab 

 and the Lithodidae bear a 

 certain superficial resemblance 

 to one another in that they 

 lead a free existence, and have re-acquired to a great extent their 

 symmetry, yet it is clear thai they have been iinl.-|M-inlent ly 

 derived from different groups of asymmetrical Hermit -crabs, ;m,| 

 that their resemblance to one another is due to convergence. 



Biryus latro (Fig. 119), a gigantic crab, frequently over a 

 foot in length, lives on land, and inhabits the 3 of coral 



inlands in the Indian and Pacific Oceans where cocoa-nul trees 



1 Alcock, luc. cit. ; Borradaile, i>. >'<>. j>. 1'JU : i. p. 64. 



B 



p IG . 



inii'i-.-iii, x 1. A, End 

 view o!' ;i. jiiccc of mangrove or liamlmo, 

 the ojH'iiin.LC nf which is closed l>y tin- 

 great chelae (c) of the 1'aguri.l ; B. tin- 

 animal ivmovi-il from its IIOHM-. 

 Alcork. i 



