550 PTERIDOSPERMS, ETC. [CH- 



Ctenopteris is in all probability very closely related to 

 Thinnfeldia and Ptilozamites. 



Dichopteris. 



This genus was proposed by Zigno^ for some large specimens 

 from the Jurassic plant-beds of Northern Italy. 



The bipinnate leaves are characterised by the great breadth of the 

 rachis which is dichotomously branched in the distal region (fig. 363) ; the 

 linear pinnae reach a considerable length. Pinnules relatively small, 

 oblong and slightly contracted at the base ; the decurrent and confluent 

 lamina forms a narrow wing to the main axis. Veins slightly divergent 

 and forked, as in Ptilozamites. 



Dichopteris visianica, Zigno. Fig. 363. 



A specimen of this species in the Padua Museum has a 

 total length of 83 cm. It has been elsewhere suggested^ that 

 a fragment figured by Zigno as a fertile example of this type is 

 probably part of a frond of the Osmundaceous fern Todites. 

 Since this opinion was expressed I have had an opportunity 

 of examining the actual specimen at Padua : the circular 

 patches described by Zigno as sori appear to be irregularities in 

 the matrix and not an original feature. 



Brongniart* instituted the genus Pachypteris for some 

 imperfectly preserved English Jurassic fossils from Whitby, 

 which he described as P. lanceolata. Specimens have since 

 been described^ from the Inferior Oolite rocks of the Yorkshire 

 coast. Brongniart described the pinnules as being without 

 veins or as possessing only a midrib. It is almost certain that 

 the apparent absence of veins in most specimens® is due to the 

 fleshy nature of the segments and that the species P. lanceolata 

 should be transferred to Dichopteris. 



Krasser^ has described a species from Cretaceous rocks of the 

 island of Lesina, off the Dalmatian coast, as Pachypteris dal- 



1 Zigno (56) A. Pis. xii. xiii. 2 geward (00) p. 170. 



3 Brongniart (28) A. p. 49. * Seward (00) p. 171. 



^ Saporta (73) A. p. 368. « Krasser (95). 



