57 



PLATE XXVIII. 



Sphenopteris. Sp. 



A most elegant Sphenopterid fern, allied to, but quite 

 distinct from, Sphenopteris obovata. The specimen is, 

 unfortunately, not to be found. It probably came from 

 the Scarborough Oolites. 



The drawing is by T. Johnson. 



The extreme difficulty of specific determination with 

 regard to the beautiful fronds which form the so-called 

 genus Sphenopteris, is too generally admitted to need 

 enlarging on here. The almost endless variety of forms, 

 which there is yet good reason to believe belong to 

 identical groups within the genus, affords a too ample 

 field to the nomenclator, and commands caution in pro- 

 posing new specific names. 



E 



