530 



MERISTIC VARIATION. 



[part I. 



814 



815. 



pair [similarly in Position D]. Maggi, L., Rend. R. 1st. Lomb., 

 1881, xiv. p. 333,^5. 



Homarus americanus : small cheliped as shewn in Fig. 182, 

 III. It bears normal dactylopodite (D) and index (7), but this 

 part is bent almost at rt. angles. From the outer angle arise 

 the parts shewn. Apparently U and D" are a complementary 

 pair of extra dactylopodites in Position D. The piece I' + I' 

 is not described ; from the figure it seems possible that it may 

 represent parts of the indices proper to D' and D". Case given by 

 Faxon, Harv. Bull, 1880—1, vm. p. 261, PI. II. fig. 2. 



Cancer pagurus : right chela as shewn in Fig. 183. This is a case 

 of some complexity. The figure will best make it clear. The dactylo- 

 podite D' is single and so also is the index P. D is a double dactylo- 

 podite, and F having teeth on two sides may be judged to be a double 

 index. But if D' and P are the normal chela they each stand opposite 



Fig. 183. Cancer pagurus, No. 815. Eight chela seen from the apex, and 

 from the outside. The lettering is arranged on the hypothesis that 1)' is the 

 normal dactylopodite, P the normal index. D, the double extra dactylopodite, 

 P', small double extra index. (From Proc. Zool. Soc.) 



the pincers to which they do not belong. Nevertheless I see no other 

 interpretation possible. (This case is curiously like that of the tarsal 

 claws in Rhizotrogus No. 786.) Specimen incorrectly described by 

 myself, P. Z. S., 1890, p. 581, fig. 2. C. 



816. Cancer pagurus : right chela in a condition not far removed from r 

 that of the last case, le S£n£chal, Bull. Soc. Zool. France, 1888, p. 123, 



figs- 



817. Uca una: a chela having complex repetition of parts somewhat 



as in No. 815. Jaeger, G., Jahresh. d. Ver. vaterl. JVaturk, 1851, xvn. 



p. 35, PL i. figs. 12 and 13. 



Perhaps of this nature is the case in Astacus fiuviatilis, Eoesel v. Kosenhof, 

 Ins.-Belust., in. Tab. L.x.fig. 28. 



(b) Two extra dactylopodites arising from normal dactylo- 

 podite. 

 *818. To this and the next division belong the great majority of 



