CHAP. XXL] CRUSTACEA : EXCEPTIONAL CASES. 



537 



Without having seen the specimen it is impossible to say much, 

 but the parts should be examined with a view to this possibility. 

 I conceive that the large spine marked by Faxon sp' stands on 



FIG. 194. Homarus americanus, No. 826. A right chela. (After Faxon.) 



the morphologically middle line between the two extra half- 

 meropodites.] FAXON, Harv. Bull. vin. p. 2G2, PL II. fig. 6. 

 *827. Astacus fluviatilis $ : large adult. i. 



Abdomen wide in comparison with 

 slender chelse: otherwise normal except 

 left chela. This was formed as in Fig. 

 195. All normal except carpopodite, 

 from which arose a fixed piece seeming 

 to be an extra misshapen carpopodite, 

 bearing three extra chelce, L', R and x. 

 [R 1 and L' are a clear pair of images L' 

 being right and left respectively. But 

 between R and the normal L there is 

 the third extra chela x. As to the 

 nature of this nothing can be said. 

 Whether it is a left or a right cannot 

 be told from fig. So far as I know, 



FIG. 195. Astacus fl 

 this case is unique. Full description 827, left chela. L, the normal. J!\ 



and measurements given in original, %TES5 

 q. V.] CANTONI, Rend. R. 1st. Lomb., nature. (After Cantoni.) 



1883, xvi. p. 77 1, fig. 



