440 BENNETTITALES [CH. 



distal ends characterised by a patch of lighter and thinner-walled 

 cells at the apex (fig. 554); the micropylar tubes are slightly 

 expanded at the summit and their epidermal cells are papillose 

 as in Williamsonia scotica (cf. fig. 563, B). Nathorst in 1909 

 adopted the name Williamsonia pecten Carr. 1 for the specimens 

 originally referred to W. Leckenby i as well as for microsporophylls 

 that he believed to belong to the same plant as the ovulate strobili : 

 but in a later paper 2 he restricts the name Williamsonia pecten 

 to the male strobili, reserving W . Leckenbyi for the ovulate forms, 

 as there is no proof that both were borne on the same plant. 

 From the evidence at present available it is reasonable to regard 

 W. Leckenbyi as a unisexual flower. In all probability the fronds 



FIG. 554. Williamsonia Leckenbyi. Micropyle and interseminal scale. 

 (After Nathorst.) 



known as Ptilophyllum pecten are the foliage of the parent-plant 

 of W. Leckenbyi, though in the absence of proof it is advisable to 

 retain both names. 



Williamsonia whitbiensis Nathorst. 



Under this name Nathorst 3 described some interesting speci- 

 mens of microsporophylls formerly attributed by him to William- 

 sonia pecten, but the discovery of additional material led him to 

 distinguish the Whitby (Lower Estuarine) fossils as W. whitbiensis, 

 retaining the name W. pecten for the type originally figured by 

 Leckenby 4 from the Middle Estuarine series at Cloughton Wyke 

 on the Yorkshire coast. In the type-specimen, 8 10 cm. in 



1 Carruthers (70) p. 694. 2 Nathorst (11) p. 19. 



- Nathorst (11) p. 9, Pis. n., m. See also Nathorst (09) p. 8, Pis. I., n. 

 4 Leckenby (64) A. 



