234 ME. HAMSHAW THOMAS ON THE FOSSIL FLORA OF [June I9I3* 



Zamites (Williamsonia) gigas (Lindl. & Hutt.). 

 ['Foss. Flor.' vol. iii (1837) pi. clxv.] 



Two specimens of fronds occur in Mr. Lane's collection that 

 can be referred to this species. They show a rachis, on the upper 

 side of which numerous pinnae are closely set. The pinna? are 

 lanceolate in shape, with entire margins tapering gradually to an 

 acuminate apex. Their bases are rounded, and they are attached 

 to the rachis by the central portion of the base, which is slightly 

 concave in form at the point of insertion. The pinnae are traversed 

 by a number of fine parallel veins. 



One of the specimens is part of a larger frond, with pinnae 

 8 to 9 cm. long and attaining a width of about 13 mm. ; the other 

 more complete example has much smaller pinnae, only 2 cm. long 

 and 5 mm. wide. The characters of both specimens are, however, 

 identical : most probably both belonged to the same species, which 

 occurs frequently at Whitby, Gristhorpe, and other localities in 

 Yorkshire. 



Another large and typical example is in the collection made by 

 the late Mr. Hawell, preserved in the Middlesbrough Museum. The 

 large form also occurs at Eoseberry Topping. 



Pig. 3. — Outlines of portions of two types of fronds referable to the- 

 aggregate species Ptilophyllum (Willianisonia) pecten. 



[A is magnified 2 diameters ; B is of the natural size.] 

 Ptilophyllum (Williamsonia) pecten (Phillips). 



[' Illustv. Geol. Yorks. pt. 1— The Yorkshire Coast ' 1829, p. 148 & pi. vii, 

 fig. 22.1 



In most of the Yorkshire fossil-plant localities series of fronds 

 are found which show a considerable range of variation among 

 themselves, but are all referable to the type of Pt. pecten. The 



