F. H. Knowlton — Jurassic Flora of Oregon. 51 



Jurassic forms a narrow band across England from Yorkshire 

 to Dorsetshire, the plant-bearing beds being especially well 

 represented in the vicinity of East Yorkshire. The area has 

 been a favorite collecting ground for English students for 

 nearly or quite a hundred years, with the result of bringing 

 together a large amount of material. Professor Seward has 

 re-studied siich of the old type material as is now available, 

 together with that of more recent date, and as a result has been 

 able to give a very full and satisfactory account of this flora. 

 The age of the Yorkshire plant beds has been very definitely 

 fixed as Lower Oolite. 



Certain of the species enumerated in the above list are very 

 characteristic of the Yorkshire flora, such for instance as 

 Cladophlebis denticulnta, Thyrsojpteris Murrayana, Ptilo- 

 zamites LecTcenhyi, Nilsonia compta, Ctenis sulcicaulis, 

 Brachyphyllum vaamillare, Pagiophyllum WiUiamsonis, 

 etc. They are, for the most part, forms not likely to be mis- 

 identified, and therefore of especial importance in the present 

 connection. 



Jurassic plants are known from a number of localities in 

 France, the more important being Mamers, D'Ethrochey, and 

 Chateauroux, in the departments of Sarthe, Cote d'Or, and 

 Indre, respectively. A considerable number of species are 

 common to these French localities and the English beds just 

 considered, while there are in common with the Pacific Coast 

 at least the following : 



Tmniopteris vittata 

 JBrachyphyllum mamillare 

 QinTcgo digitata. 



A single species (Sagenopteris Goppertiana) has been 

 reported b}' Zigno from the Lower Oolite of Italy. 



It is of interest to note that there are two species — Ptero- 

 phyllum contiguum and P. Nathorsti — found in the Oregon 

 beds that have previously been reported only from the Kwei- 

 tschon beds of China. According to Schenk this horizon can- 

 not be older than Lower Jurassic, and, as Fontaine has stated, 

 since the beds contain Podozainites lanceolatus and Nilsonta 

 comp/ta, it is most likely that the age is Lower Oolite, certainly 

 not younger. PterophyUum oeqttale has been noted by Schenk 

 in the Tumulu coal fields of China, in beds of Lower Oolitic 

 age. 



In the Kaga strata of Japan, which Yokayama refers to the 

 Lower Oolite, we have Nilsonia nipponensis, a species repre- 

 sented by several fairly well preserved examples in the Ore- 

 gon beds. 



