532 



MKRISTIC VARIATION. 



[PART i. 



The various simple forms taken are illustrated by the eight 

 case> shewn in Fig<. 1S4, is:, and 186. It will be seen that when 

 such extra processes arise on the toothed border of the dactylo- 

 podite they turn th.-ir * mouth borders to each other, but when 



II 



HI 



FKI. 186. llonianix nnu'ricanus. Three chela} whose dactylopodites bear double 

 extra dactylopoditos. I. A left. II. A left. III. A right. Ii, normal right. 

 L, normal IH't. A 1 ', extra right. L', extra left. (From Faxon.) 



they arise on the smooth border they turn their toothed borders 

 to each other, thus fulfilling the conditions of the Scheme given 

 at p. 4S1. Though from the close agreement between the three 

 prongs in some of the specimens it is not always possible to 

 tell the normal dactylopodite with certainty, it will be seen that 

 in these the rules hold whichever of the two possible prongs be 

 supposed to be the normal. 



819. Astacus leptodactylus : left chela has dactylopodite as 

 -hewn in Fig 1ST, II. Presumably D is the normal pushed out 

 of place, and D' and D" are the two extra dactylopodites. They 

 are so placed that none meets the index. KAROLI, J., Term. 

 FH:i't,-l.; 1ST 7, I. p. >:{, PI. II. 



