26 



GINKGOALES 



[CH. 



Ginhgoites whiibiensis (Natliorst). 



This name was proposed by Nathorst^ for a leaf from the 

 Jurassic rocks of the Yorkshire coast in the British Museum similar 

 to some of the smaller forms referred to G. digitata but characterised 

 by the deltoid form of the lamina, its deep dissection into six 

 more or less pointed segments, three on each side of a broad median 

 V-shaped sinus, and by the small size (1-5 cm. broad and 2-5 cm. 

 deep) of the lamina. It is hardly possible to decide whether this 

 and similar small leaves should be regarded as varieties, e.g. G. digi- 

 tata var. polaris, or assigned to a distinct species. Fontaine^ com- 

 pares some leaves figured by him from Oregon as Ginkgo sp. with 

 Nathorst's species, but they are probably nearer to the examples 

 described by Nathorst and others as G. polaris. A small bilobed 

 leaf figured by Raciborski^ from Rhaetic beds near Cracow as 

 Ginkgo aff. whitbiensis is more likely to be a young leaf of the 

 Fern Hausmannia. 



Fit). 642. Oinkgoites Obrutschewi. (A, nat. size.) 



Ginkgoites Obrutschewi Seward. 



This species, named after Prof. Obruts»hew who made a col- 

 lection of plants from Jurassic rocks in Chinese Dzungaria* on 

 the western border of Mongoha (lat. 85° N. long. 45° E.), agrees 

 fairly closely with some forms of G. digitata. The lamina is deeply 



1 Nathorst (80) A. p. 74; Seward (00) B. p. 261, PI. ix. fig. 8, 



- Fontaine in Ward (05) B. PI. xxxiv. 



= Raciborski (91) PI. iv. fig. 13. " Seward (11) p. 46, Pis. iii.— vii. 



