PLATE I 



FIG. 28. 



Scale of Hijypnrchia Janira. 





of Poilura plumbea : A, large 



O strongly marked scale; B, small scale 

 more faintly marked; c, portion of an 

 injured scale, showing the nature of the 

 markings. 





Fio. 29. 



Ple.uro.ngmn artgulntum : A, entire frustule, as seen 

 under a power of 500 diam.; B, hexagonal aerolation, 

 as seen under a power of 1300 diam.; c, the same, 

 as seen under a power of 15,000 dinm. 



