DIPTERIBIIfiE. 89 



52,548. Numerous fertile pinnules showing tie son, but no 

 individual sporangia ;. edges of pinnule revolute as in Matonia 

 pectinata. 



Collyweston. Morris Coll. 



52,870. Several fragments of fertile pinnules crowded together 

 «,s i£ deposited in an eddy ; circular sori clearly shown. 



Ponton, Lines. Sharp Coll. 



Other specimens .•—52,584, 52,869, 82,439 (Stamford). 



Sharp Sf Mheridge Colls. 



Family DIPTERIDINiE. 



In this family of Leptosporangiate ferns are included the recent 

 genus Dipteris, represented by four species in India, the Malay 

 Peninsula, and elsewhere, and several Ehsetic and later Mesozoic 

 ■species referred to Dictyophyllum and other genera. Like the 

 Matoninese, the Dipteridinae ^ must be looked upon as survivals 

 from the Mesozoic era, when they were widely spread throughout 

 Europe and constituted prominent members of Eheetic and Jurassic 

 floras. 



Genus DICTYOPHYLLUM, Lindley & Hutton. 



[Foss. Flor. ii. pi. civ. 1834.] 



It is often difficult to decide between the generic names Dietyo- 

 _phyllum and Protorhipis in naming imperfect specimens of fronds, 

 and it is by no means improbable that the leaves referred to both 

 genera may be generically identical. A comparison of various 

 types of Dipteris fronds, as shown in the drawings published in 

 a paper on recent and fossil Dipteridinae by Miss Dale and myself, 

 demonstrates the futility of attempting to discriminate between 

 fragments of Mesozoic leaves by the employment of different 

 generic names. In cases where the material admits of a fairly 

 complete diagnosis the employment of distinctive names may serve 

 .a useful purpose, but a specimen such as that represented in Text- 

 fig. 8 is too imperfect to identify within narrow limits. 



1 Seward (00), p. 118 ; Seward & Dale (01), p. 36. 



