JVILLIAMSONIA. 185 



11,020. PI. VII. Fig. 6. 



Part of a frond 21 cm. in length. The small piece shown in 

 "the figure illustrates the rounded form of the pinna base and 

 the median concavity, indicating the existence of a callus or basal 

 thickening at the point of attachment to the rachis. It shows 

 also the slightly spreading veins, which throughout the greater 

 part of each pinna follow a course approximately parallel to the 

 long axis of the pinna. 



Oolitic Shale, Gristhorpe Bay. Mantell Coll. 



V. 2609ff. PI. VI. Fig. 2. 



Well-preserved examples of the stem of Williamsonia gigas are 

 rarely met with ; the figure represents the only specimen in 

 the British Museum Collection iu which any surface-features are 

 shown. A similar specimen may be seen in the "Woodwardian 

 Museum, Cambridge (Leckenby Coll., No. 203). The persistent leaf- 

 bases are shown as spirally disposed projecting areas recalling the 

 appearance of recent Cycadean stems ; the concave termination at 

 the top of the specimen probably represents the position of 

 a flowering axis such as we know were borne by the stems of 

 Williamsonia. The stem measures 9 cm. in length and 5 '5 in 

 breadth. Fragments of fronds and flowers are associated with this 

 piece of stem, and on the reverse side of the specimen there is 

 a good example of a disc like that of 38,785 (PI. VIII. Fig. 1). 



Yorkshire. Bechles Coll. 



V. 3514. PI. VII. Fig. 5. 



A part only of the specimen is represented in the flg-ure ; there 

 is not enough of the frond preserved to enable one to be quite 

 cure as to its identity with Williamsonia gigas or Otozamites 

 aeuminatus ; but the rounded edges of the pinnae bases and the 

 absence of any definite Otozamites ' ear ' point to Zamites as 

 the generic type rather than to Oto%amites. Cf. Otozamites 

 Xlvpsteini (Dunk.) as flgured in pi. vii. of the WeaUen Flora.^ 



V. 2722. Good examples of long fronds, which illustrate the 



Seward (95), pi. vii. 



