XXXVIl] 



WILLIAMSONIA 



441 



diameter, there are 15 linear segments coalescent basally into 

 a thick cup differing from that of W. spectabilis in the absence of 

 a stalk (figs. 555, 556). A more important distinctive feature is 

 the production of synangia on the simple sporophylls (figs. 556, B ; 

 565, B) and not on special fertile segments as in W. spectabilis 



Fig. .555. Williamsonia whitbiensis. (After Nathorst; | nat. size.) 



Pig. 556. Williamsonia whitbiensis. A, male flower. B, sporophyll with synangia. 



(After Nathorst.) 



(fig. 552). The inner face of each sporophyll, as seen in im- 

 pressions, shows two regular rows of small depressions, one 

 on each side of the median line; these become gradually 

 smaller towards the base of the cup-Uke disc (figs. 555, 556). 

 On the actual carbonised surface of the inner face of the cup 

 small and transversely elongated projections take the place of 



