chap, xxi.] 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 



% E + L 



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



the morphologically middle line between the two extra half- 

 meropodites.] Faxon, Harv. Bull. vm. p. 262, PI. II. fig. 6. 

 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! 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 '^^^^LJI^X 



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 fluviatilis^o. 



this case is unique. Full description 82 ?> left chela. L, the normal. lr 



j , • • ■ ■ i L', presumably extra right and left 



and measurements given m original, ch ' el ^ x> ext ^. a chela b f uncertain 



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



1883, xvi. p. Til, fig. 



