320 



DIPTERIDACEAE 



[CH. 



leaved Ferns, with more or less distinctly ascending, helicoid, dichopodial 

 structure of the lamina, the segments of which were pinnatifid like Matonia 

 pectinata (see Vol. I, Fig. 82, C, D). These he suggested might be placed as 

 a sub-family of the Dipteridaceae. On the other hand, Hmismannia, as 



F'g- 578- Hatismannia dichotoma, showing the habit-similarity to the narrower- 

 leaved species of Dipteris. (Specimens from the late Dr Marcus Gunn's collection 

 of Upper Jurassic plants. Sutherlandshire : very slightly reduced.) (From 

 Seward.) 



Halle has recently shown, may safely be more closely related with Dipteris 

 itself. In H. dicJiotonia the leaf-structure closely resembles that oi D. Lobbiana 

 (Fig. 578), while that of an un-named species of Hansviannia (Fig. 579), 

 with a more nearly entire lamina, is like that of D. conjugata. But it is in 



