PLATES I-III. 



All the figures here presented were drawn with the aid of the 

 camera lucida and then redrawn, magnified nearly two times, with 

 the aid of another camera apparatus. Various magnifying powers 

 were employed at diff'erent times and will be specified in connection 

 with the figures. The plates were then all reduced in the reproduc- 

 tion, to their original size. 



( 57 ) 



