of the Common Shore-Grab, 



205 



does not develop the three lobes, as in the adult form, until 

 after several moults. They are first indicated by a slight 

 depression on each side of the median line ; the frontal margin 

 after the 6th ecdysis is more undulating than in any of those 

 preceding it, and after the 7th ecdysis the three lobes appear; 

 but several more ecdyses have to be gone through before they 

 obtain their normal proportions. From fig. 2 to fig. 7 the 

 carapace assumes its normal shape by a gradual increase in its 

 width compared to its length. With each successive moult 

 the lateral toothed margins are pushed more forward, and 

 the teeth become more prominent. 



In the following Table I have represented the measure- 

 ments of forms A and B at each ecdysis from the Megalopa 

 onwai'ds in millimetres, the figures above the line representing 

 the length of the carapace and those below the width. I 

 have then endeavoured to fit in measurements of ten other 

 individuals which have been collected in the adult form, in 

 in order, if possible, to form an approximate idea of the number 



