528 



MERISTIC VARIATION. 



[part I. 



compounded extra points in Position J). Duns, Proc. jR. PJiys. Soc. 

 Edin., ix. p. 75, PL 



Fig. 181. I. Lithodes arctica, normal terminal joint of ambulatory leg. 

 II. Second right leg of No. 809. (Both after Herklots.) III. Carcinus mcenas, 

 No. 811, second ambulatory leg. (After Duns.) P, normal terminal point. P', 

 P", extra terminal points in Position D. 



B. Chelate Appendages. 



(a) Two extra dactylopodites and double extra index. 



812. Eriphia spinifrons $ : specimen of unusually large size, 

 normal but for left chela shewn in Fig. 182, I and II 1 . The 

 chela bore normal left dactylopodite, LD, and index, LI ; also, 

 upon pollex-border the structures shewn. These consisted of two 

 dactylopodites, R'D, L'D, working opposite each other on a com- 

 pounded double index, R'l\ L'l, which had two toothed borders, 

 one for each of them. This is therefore a pair of chelae repeated 

 in Position D [if indeed the dactylopodite mark the dorsal surface]. 

 Taken from Herklots, Arch, neerl., 1870., v. p. 412, PL XI. 



1 In connexion with this case Herklots states that the rt. chela in the normal 

 is the larger and otherwise differs from the left (1 in 8 being reversed in this 

 respect). It does not seem from the figure that there was such differentiation 

 between the extra pair, but in future cases this point should be looked for. 



