26 



GINKGOALES 





GinJcgoites whitbiensis (Nathorst). 



This name was proposed by Nathorst 1 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. diqitata but characterised 



*J 



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 2 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 3 from Rhaetic beds near Cracow as 

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

 Fern Hausmannia. 



FIG. 642. Ginkgoites Obmischewi. 



Ginkgoites Obrutschewi Seward. 



This species, named after Prof. Obrutschew who made a col- 

 lection of plants from Jurassic rocks in Chinese Dzungaria 4 on 

 the western border of Mongolia (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, 



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



3 Raciborski (91) PI. iv. fig. 13. 4 Seward (11) p. 46, Pis. m. vn. 



