24 THE RARITAN FLORA. 



Gleichenia giesekiana Heer. 



Gleichenia microniera Heer. 



Gleichenia Zippei Heer. 



Podozamitcs Knowltoni Berry. 



Podosamites lanceolatus (L. & H.) F. Braiin. 



Sequoia Reichenbachi (Gein.) Heer. 



Thuyites Mcriani Heer. 



Of these the ferns and the gymnosperms, which make up the 

 bulk of the Hst, are to be regarded primarily as Lower Cretaceous 

 types which survived into the Upper Cretaceous. Among the 

 generic types of ancient lineage which are represented in the 

 Raritan, are Baiera, primarily a Triassic and Jurassic genus, 

 the Raritan species of which is closely related to forms found in 

 the Older Potomac, Willianisonia a Jurassic and Lower Cre- 

 taceous genus, Brachyphyllum a Triassic and Jurassic genus, the 

 Raritan species of which is closely related to and clearly de- 

 scended from Brachyphylhini crassicaide Font, of the Patapsco 

 formation, and finally Czekanozuskia a Triassic and Jurassic 

 (chiefly Oolitic) genus. 



In no part of the world has a single representative of any of 

 these genera been found as late as the Senonian, and it is sig- 

 nificant that two of them, Brachyphyllum^ and Czckanowskia 

 furnish their last known record in the Cenomanian of Portugal, 

 while the last occurrence of Baiera and Williamsonia^ is in the 

 Cenomanian Atane beds of Greenland. 



When the Raritan flora is compared in detail with ihe Pa- 

 tapsco flora of Maryland and Virginia, many common features 

 are brought out which at first sight tend to be obscured by the 

 preponderating dicotyledonous element in the former. In addi- 

 tion to the identical or closely related forms previously men- 

 tioned, we find among the dicotyledons five Raritan genera 



^ The Raritan species B. macrocarpum Newb. is recorded from the follow- 

 ing American horizons: Montana Group of Wj'oming, Dakota Group of 

 Kansas, Magothy formation of Long Island, New Jersey and Delaware, the 

 Middendorf of South Carolina (?). the Bladen of North Carolina (?), and 

 the Patoot beds of Greenland (?), the former of course of "Senonian age. 



'A questionable species is recorded from the Dakota group and another 

 species occurs in the Magothy formation. 



