XILSSONIA. 



225 



broad shallow groove, which might suggest the lateral attachment 

 of the lamina characteristic of Pterophyllum fronds. 



The largest examples I have met with are in the Whitby 

 Museum, some of which have a length of over 40 cm. and 

 a breadth of 9cm. (vide Text-fig. 40). A large frond, with 

 narrow segments, 31 cm. in length, may be seen in the Scarborough 

 Museum. Good specimens are represented also in the Leckenby 

 Collection, Cambridge, the Museum of Practical Geology, London, 

 and elsewhere. A Scarborough specimen in the Natural History 

 Museum, Paris, bears the name Niksonia Williamsonis, the original 

 specific designation proposed by Brongniart. 



A B C 



FIG. M.Nikiio,<iii. cousin (Phill.). 

 A and B. No. V. 2894. C. ]S T o. 40,469. (Xat. size.) 



Nilssonia compta, characteristic of the Inferior Oolite vegetation, 

 appears to be practically identical with some, at least, of the 

 fronds of KhaBtic age described by Schenk, 1 Nathorst, 2 and] others 

 as W. polymorpha ; this close resemblance affords one of many 

 instances of the marked agreement between the Ehaetic and Inferior 

 Oolite floras. 



1 Schenk (67). 



Nathorst (78 1 ), (78 1 ). 



