126 DICTYOPH YLLTJM. 



V. 2724. PI. XVIII. Fig. 1. 



A good specimen representing the apical portion of a pinna; 

 at the apex the pinna is strongly dentate, and the pointed entire 

 segments become rapidly longer towards the lower part of the 

 leaf, which may he described as pinnatisect with linear tapering 

 segments. The whole specimen has a length of 17 -5 cm., but the 

 lowest part is not shown in the figure. Prominent lateral veins 

 are given off from the central axis of the pinna, and from these 

 arise smaller anastomosing veins. 



The segment shown in Fig. 3, PI. XIII. is, in all probability, 

 specifically identical with the present specimen, and belongs to the 

 lower part of a deeply dissected pinna, of which Fig. 1, PL XVIII. 

 represents the apical portion. SecTcles Coll. 



Text-fig. 17 (Whitby Museum, No. 2360). 



This unusually good specimen from the Whitby Collection is no 

 cloubt the one referred to by Nathorst 1 in his notes on the Jurassic 

 Flora of England ; he compares it with Clathropteris platyphytta, 

 Brongn., and adopts the name C. whitliensis, which Brongniart 

 suggested, but never published, for the Whitby specimen. 



A comparison of specimen V. 2724 (PI. XVIII. Fig. 1) with 

 Text-fig. 17 at once brings out the close agreement between one 

 of the dentate divisions of the frond shown in the figure and the 

 portions of a pinna represented in Fig. 1, PL XVIII. The Whitby 

 specimen is an example of a comparatively small frond clearly 

 illustrating the characteristic method of branching of the main 

 veins, which agrees with that in the recent genus Dipteris. The 

 commoner specimens of Dictyopliyllum are merely portions of pinnse 

 or the ultimate segments of pinnse. 



The spotted appearance shown in Fig. 17 is due to the presence 

 of small patches of carbon ; no definite trace of sporangia can be 

 detected. 



V. 2891. Text-fig. 18. 



An imperfectly preserved frond similar to the Whitby specimen 

 (Fig. 17), but without the lower portion of the leaf where the 

 several pinnse converge into a common lamina traversed by radiating 



1 Nathorst (80 1 ), p. 83. 



