180 WILLIAMSONIA. 



prevents us speaking with certainty as to the floral characters 

 of Williamsonia gigas. During the last few years numerous- 

 silicified stems of Bennettites have been discovered in North American 

 heels, and a preliminary account of the flowers of some of these 

 species by Mr. Wieland, 1 of Newhaven, leads us to look forward 

 with considerable interest to the publication of his more detailed 

 work. One of the most interesting points brought to light by 

 Wieland's work concerns the nature of the male reproductive 

 organs. I am indebted to the courtesy of this investigator for 

 a section through the male sporophylls of a flower, which shows 

 very clearly several sporangia containing microspores (pollen- 

 grains). The microspores bear a striking resemblance to those- 

 of recent Cycads. 



In describing the specimens of Williamsonia gigas in the British 

 Museum, I have drawn attention to several features which enable 

 us to obtain a fairly comprehensive view of the external characters 

 of this interesting type of the Bennettiteae. 



The specific name Zamia Mantelli instituted in 1828 by Brongniart 

 was afterwards quoted by this author as a synonym of Zamites 

 gigas, L. & H. For this reason, and because the latter name has 

 been generally adopted, the older specific designation is discarded. 

 The earliest figure of an English specimen of this species was 

 piiblished by Young & Bird in 1822. 3 The fronds of Williamsonia 

 gigas (L. & H.) represent a type of Cycadean foliage which was- 

 abundant and widely distributed during the Jurassic period ; it is 

 very difficult to decide which of the many pinnate fronds of the 

 Zamites type should be included under W. gigas. Some at least of 

 the fronds described by French authors from Jurassic rocks are no 

 doubt specifically identical with the Yorkshire plant, but it is not 

 improbable that other species, not included in the above synonymy, 

 might reasonably be referred to the English type. A collection 

 of Yorkshire specimens in the Natural History Museum, Paris, 

 contains some of the most important examples of Williamsonia 

 gigas, and an examination of these fossils has aided me considerably 

 in forming an opinion as to the close affinity of Williamsonia with 

 Bennettites. 



1 Wielaud (99-) . 



z Young & Bird (22), pi. ii. fig. 2. The original specimen (No. 2344) is in the- 

 Whitby Museum. 



