XXXVII] 



WILLIAMSONIA 



437 



discovered by Prof. Nathorst in the Lower Estuarine series of 

 Whitby; it has also been obtained from beds of the same age at 

 Marske in the Cleveland district of Yorkshire 1 . Williamsonia 

 spectabilis, though indubitably a male organ, has not been found 

 attached to a stem, and there is no decisive evidence as to its 

 connexion with a particular species of frond. Nathorst believes 

 that it belongs to the plant which bore the leaves known as 



FIG. 551. Williamsonia spectabilis and leaves of Ptilophyllum pecten. (After 

 Nathorst; f nat. size.) 



Ptilophyllum pecten, an opinion based chiefly on association. 

 The more complete specimens consist of a broad funnel-shaped 

 organ prolonged below into a slender stalk and divided at the 

 margin into several linear-lanceolate segments (microsporophylls) 

 the apices of which were rolled inwards like young fern-fronds 

 (figs. 551, 552). The synangia agree closely in form and in such 

 structural features as can be made out from cuticular preparations 

 with those described by Wieland in American species of Cyca- 

 deoidea ; they are slightly reniform, 5 6 mm. long and 2 mm. 

 broad and divided into several loculi by transverse partitions 



1 Thomas (13 2 ) p. 230, PL xxiv. figs. 13. 



