41 



102 



m 

 > 



n 

 in 



o , 



•^100 



> 



98 



BIDENTATA alt 

 OBSCURA alt. 



■BIDENTATA diam 

 OBSCURA diam. 



It seems hardly credible that such a correspondence of relative sizes 

 in the different loci as is shown in diagram 2 should be of fortuitous 

 internal origin rather than an expression of environmental circum- 

 stances. The two species being of similar habits, it is not unlikely 

 that they would be afiected in the same way by similar conditions, 

 and as far as their size is concerned such appears to be the case 

 in the five cases under consideration. 



Calculated on the (doubtless erroneous) assumption that the measured 

 diameter = the diameter of the base of a cone and the measured altitude its 

 height. 



