XXXVII] WILLIAMSONIELLA 467 



Mr Hamshaw Thomas 1 described some specimens from the 

 Middle Jurassic beds of Marske in Yorkshire which he suggested 

 might be pieces of a Wielandiella stem. Additional material 

 was subsequently found and this enabled Thomas to produce 

 evidence in favour of connecting the branched vegetative axis 

 with bisporangiate strobili and the fronds of Taeniopteris vittata. 

 For the stems and flowers the new designation Williamsoniella 

 has been proposed. Further research will no doubt show that 

 the Wielandiella type of stem was not exceptional in Rhaetic 

 and Jurassic floras. 



Nathorst 2 suggests the possibility that some specimens from 

 the Solenhofen Slates described by Thisel ton-Dyer 3 as Condylites 

 squamatus may be allied to Wielandiella. The generic name 

 Condylites was suggested by the elbow-like branching of stems 

 which bore imperfectly preserved and apparently terminal cones ; 

 the surface of the branches is covered with the scars of leaves. 

 The resemblance to Wielandiella is, however, slight and it would 

 seem more probable that the Solenhofen fossils are Coniferous, 

 though, as Nathorst says, the supposed scale-like 'leaves' may 

 be scars of Cycadean fronds. 



Wieland 4 records the occurrence in Mexico of stems similar 

 to those of Wielandiella associated with some Otozamites fronds. 



WILLIAMSONIELLA. Thomas. 



This genus was instituted for specimens discovered by Mr 

 Hamshaw Thomas 5 in the Middle Estuarine series of the Middle 

 Jurassic plant-bed at Gristhorpe on the Yorkshire coast, and the 

 genus is recorded also from the Cleveland district in the same 

 county. Williamsoniella occurs in those parts of the Gristhorpe 

 bed where fronds of Taeniopteris vittata are abundant. 



Williamsoniella coronata Thomas. 



The type-species is represented by fertile shoots consisting of 

 a central axis bearing both megasporophylls and microsporophylls 

 (figs. 569, 571, A). Below its crown-like sterile apex the pyriform 

 peduncle is covered with small interseminal scales and ovules 



1 Thomas (13 2 ), p. 239. 2 Nathorst (02) p. 16. 



3 Thiselton-Dyer (72). 4 Wieland (11) p 458. 



5 Thomas (15 2 ). 



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