THE JURASSIC FLORA OF SUTHERLAND. 



677 



which are fairly numerous, are surrounded by a ring of flatter cells (fig. 7, B) ; the actual 

 form of the guard-cells is not seen, but a hole in the film represents the external 

 stomatal pore. Drawings like that in fig. 7, B, have been published by Schenk. # 



Text-Fig. 7. — Thinnfeldia sp. 



ab. Actual size of the fragment enlarged in fig. A. 



B. Stomata from one of the leaflets. 



C. Outline of cells from the rachis. (Gunn collection. ) 



Thinnfeldia arctica Heer. (PL II. figs. 37, 37A ; PL IV. fig. 68.) 

 1875. Heer, Flor. Foss. Arct., vol. iii., 2, p. 123, pi. xxxv. figs. 11-16, pi. xxxvi. fig. 105. 



Fig. 68, PL IV., shows the impressions of a pinna fragment on which the bluntly 

 terminated segments are rather more crowded than in T. rhomboidalis. The same 

 type with more distinct venation is represented in figs. 37, 37A, PL II. This fragment 

 bears a superficial resemblance to Cladophlebis, but in Thinnfeldia the secondary veins 

 are given off at a more acute angle ; moreover, the lamina is often easily detachable from 

 the matrix, which may denote a more strongly cuticularised epidermis. These specimens 

 agree closely with Heer's type-specimens from the Upper Jurassic of Spitzbergen f 

 and with Nathorst's specimens I from the same locality. 



* Schenk (67), pi. xxvii. t Heer (75), pis. xxxv., xxxvi. I Nathorst (97), pi. i. figs. 23, 24. 



