1894.] MICROSCOPICAL JOURNAL. 173 



This belongs to the Eocene period before the Oligo- 

 cene Tertiary. 



The California Infusorial stratum which was discovered 

 by Bailey at San Pablo, near San FranciscOj and near by 

 which I lived nearly two years, and the Monterey and 

 Santa Monica, is Oligocene though ranked as Miocene by 

 most geologists. 



Cooke gives an analysis of the Drakesville, N. J., In- 

 fusorial stratum, which is as follows : 



Silica 80 C>(i 



Alumina .' ?>.H\ 



Lime 58 



Loss on iguitiou (orgauic matter and water)... 14.01 



99.09 



It belongs to the iceberg period. 



In Mexico, near Socorra, within 12 miles of the city is 

 a vast layer of Infusorial earth which is Eocene also. 

 It seems to belong to the Occidental Sea, but it has not 

 been investigated as yet. 



Now we se-i that the Eocene does not contain any 

 alumina and is not a clay, strictly speaking. But the 

 iceberg period strata, both in Bohemia and in New 

 Jersey are clays made by the breaking down of tlie 

 granite. This is a difference between those from the 

 Eocene and iceberg strata, and it has been rendered solid 

 by the solution of the silica and not by the clay. 



I do not know of them except the Franzenbad, which 

 has been analyzed, and which is also known as Soos. 

 In contains too large a quanity of Campylodiscus. In 

 the Eocene of Utah lake and of Mono lake and of Pyra- 

 mid lake, there is present a Surirella utahensis of Ehren- 

 berg. But this is Surirella striatula of Turpin, 1828. 

 It is the Navicula (?) striatula of Ehrenberg, 1838, but 

 is a true Surirella. Surirella striatula is brackish and 

 marine. It is also fresh water in one " Keiselguhr von 

 Franzenbad." In fact, it sometimes occurs circular in- 

 stead of elongated, and looks as if it were passing into 



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