Geological Society. 62o 



PROCEEDINGS OF LEAUXED SOCIETIES. 



GEOLOGICAL SOCIETY. 



February 25th, 1903.— Prof. Charles Lapworth, LL.D., F.R.S., 

 President, in the Chair. 



The following communication was read: — 



'On the Occurrence of Dictyozamites in England, with Kemarks 

 on European and Eastern Floras.' By Albert Charles Seward, 

 Esq., M.A., F.R.S., F.L.S., F.G.S., Fellow of Emmanuel College, 

 Cambridge. 



The specimens described as a new species of Dictijozamites wero 

 obtained from a bed of ironstone, low down in the Estuarine Series, 

 on the northern face of tho Upleatham outlier, near ^larske-by-the- 

 Sea, by the Eev. John Hawell, F.G.S. The genus is also found in the 

 Rajmahal Series of India, in Central Japan, and at Bornholm, Its 

 probable taxonomic position is best expressed by placing it as a 

 member of the Cycadophyta. 



The Author proceeds to a comparison of the Bornholm, Indian, 

 Japanese, and English floras ; and as resemblances are masked by 

 the use of different generic or specific names for plants which are 

 either identical or represent closely-allied members of the same 

 family, a special list of these floras has been prepared, in which, 

 while the names at present in use are indicated, it is pointed out 

 where obscured identities or resemblances exist. From this com- 

 parison the Author concludes that there was a greater similarity 

 between the vegetation of Eastern and AVestern regions, during 

 part at least of the Mesozoic Era, than is usually admitted ; while 

 the differences between Mesozoic floras of approximately the same 

 geological age are for the most part slight and unimportant, when 

 their wide geographical separation is considered. Equisetaceous 

 plants are practically ubiquitous : several ferns of apparently the 

 same species occur in the Far East and in "Western Europe ; cycada- 

 ceous plants are represented by cosmopolitan types, and the same 

 may be said of the genus Araucarites and other members of the 

 Coniferae. The most noteworthy exceptions are aflbrded by the 

 Mesozoic representatives of the two isolated recent ferns Mnionia 

 and Dipteris ; these two families — each with a surviving genus — 

 played a conspicuous part in the vegetation of the Rhtetic and 

 succeeding Jurassic Epochs in Europe, and to a less extent in Xorth 

 America, but there ai'e no satisfactory records of their existence in 

 India or Japan. A similar state of things is illustrated by the 

 Ginkgoales, the class of which the ' maidenhair-tree ' of China and 

 Japan forms the solitary survivor ; the abundance of both Ginlr/o 

 and Bciiera in the Mesozoic of Europe is in striking contrast to 

 their almost complete absence in India. 



Ann. dt- J%. r^\ Hist. Ser. 7. Vol. xi. 43 



