OF DENISOX UNIVERSITY. 1x5 



Diatomos, a through-cutting), which takes place, not transversely, but 

 longitudinally; and the lines which mark its progress are almost al- 

 ways visible in them. In this process of division new valves are 

 formed along the line of division, the old ones remaining on the outer 

 sides, and each new diatom cell having an old valve and a new one. 

 But sexual reproduction takes place by conjugation and by the forma- 

 tion of auxospores, which restores periodically the normal size of the 

 species. 



Diatoms are quite abundant in the vicinity of Granville, Ohio, 

 some of them being rare specimens. The following list I have iden- 

 tified for the most part, by recourse to the photographic plates from 

 Aldolf Schmidt's "Atlas der Diatomaecen-Kunde."' 



Cyjnbellce. gastrotdes, K. 



Navicula poly strict a, Gru. 



Navicula polystricta, (var. ) circumstricta, (irunow. 



Navicula seutclloides, Sm. Domb. 



Navicula Cynt/iia, A. S. Java. 



Navicula cuspidata. t 



Navicula borealis.X 



Navicula cryptocephala.X 



Navicula entomo7i.X E. 



Navicula biceps. E. 



Navicula latissima, Greg. + 



Navicula consi mills, A. S. 



Navicula lanceolata, K. 



Navicula brevis, Greg. 



Navicula latissima, (type), A. S. 



Navicula longa, Cireg. 



Nit zs cilia coat-eta la. % 



Pleiirosigma Spencei'i, %. 



Gomphonema acuminatum, E. 



Fragilaria lanceolata. %. 



Diatoma meridian circula re. % 



Friceratium solenoccj'os, E. 



Friceratium Jensenianum, ( irunow. 



Friceratium venosum, Brighton. 



J. Not typical, but probably a variety. 



X. Identified by plates in Indiana Geol. Rep. Vol. II 



