202 DISCOVERY REPORTS 



a Surirella there is a true canal-raphe, supported above the surface of the valve by a 

 wing-like projection ; a series of capillary tubes through the supporting columns of the 

 wing are filled with protoplasm and so maintain contact between the inner cell contents 

 and the medium in which the diatom lives. In addition there is a pseudoraphe upon 

 each valve in the polar axis. 



This classification differs in no material respect from that of Schiitt's with the excep- 

 tion that it does not recognize the initial division into two groups according to the so- 

 called centric and pennate construction. 



The following list shows the systematic position assigned to the genera examined in 

 the preparation of this paper. 



ALGAE 



Class BACILLARIOPHYCEAE 



Melosira Agardh 



Skeletonema Greville 

 Stephanopyxis Ehrenberg 



Thalassiosira Cleve 

 Coscinoscira Gran 

 Lauderia Cleve 



Coscinodiscus Ehrenberg 

 Charcotia M. Peragallo 

 Planktoniella Schiitt 



Hemidiscus Wallich 



Stictodiscus Greville 



Order BACILLARIALES 

 Suborder DISCINEAE 



Family COSCINODISCACEAE 



Subfamily MELOSIROIDEAE 



Hyahdiscus Ehrenberg 



Subfamily SKELETONEMOIDEAE 

 Detonula Schiitt 



Subfamily THALASSIOSIROIDEAE 



Schroderella Pavillard 

 Bacteriosira Gran 



Subfamily COSCINODISCOIDEAE 



Gossleriella Schiitt 

 Schimperiella Karsten 

 Actinocyclus Ehrenberg 



Family HEMIDISCACEAE 

 Subfamily HEMIDISCOIDEAF 



Family ACTINODISCACEAE 



Subfamily STICTODISCOIDEAE 



Arachnoidiscus Ehrenberg 



