262 



S. J. Smith — Tropical and Sub-tropical 



ordei' to give the readiest means of comparison, the breadth and the 

 breadth of the front are given first in millimeters and then, in the 

 same divisions of the table, in units of the length of the carapax. 



The limits of variation as shown in the table are found in Atlantic 

 specimens. Considering the considerable variation in the proportions 

 of specimens of about the same size, the differences in this respect 

 between the smallest and the largest specimens measured is surpris- 

 ingly small. The carapax appears to grow proportionally very 

 slightly narrower with increasing size, as I have noticed in a few 

 other species of Grapsoidea, though the reverse is usually the case in 

 nearly all groups of Brachyura, and is what Ave should naturally 

 expect from the increase, during the early growth of the animal, in 

 the functional importance of the branchiae 



The measurements given in the last line in the table are of a 

 parasited specimen with one of the branchial regions considerably 

 distorted. 



