T^NIOPTERIS. 123 



are certain distinctive features in the venation of the two genera 

 which enable us to distinguish them in most instances. Heer's 1 

 figures of Nilssonia orientalis, Hr., probably represent a Tceniopkeris; 

 the apex of the leaf is like that of T. Beyrichii, Schenk, and 

 the venation corresponds to T. Dawsoni, sp. nov. 



The genus Oleandridium was founded by Schimper to include 

 ferns with "Frondes simplices, lanceolato-elongatae vel Iingulata3, 

 coriaceae. Fructificatio Aspidiacearum ? " 2 In Zittel's " Palaeo- 

 phytologie " 3 this genus is described as differing from Tceniopteris 

 by its more distinctly horizontal and stronger lateral veins which 

 end in a marginal vein, and by the longer and more elliptical form 

 of the leaf. Another writer 4 speaks of Oleandridium as comprising 

 those leaves of the nervation type Tceniopteridis which have simple 

 lamina? not pinnately divided. 



It is unnecessary to suggest that there is a considerable amount 

 of confusion and uncertainty about the two genera, Tceniopteris, 

 Brong., and Oleandridium, Schimp. The latter name leads one 

 to suppose some well-established affinity with the genus Oleandra. 

 If specimens with fructification agreeing with that of the recent 

 genus are found they might with advantage be so named, but to 

 designate such a form of leaf, common among fossil ferns and 

 common in recent genera, by names which imply affinities founded 

 on external form and venation is utterly misleading. In adopting 

 Schimper' s genus for a Chinese plant, Schenk 5 expressly states 

 that he does not mean to convey the idea of a relationship with 

 the recent genus Oleandra, but he makes use of the term Olean- 

 dridium for the purpose of indicating a probable difference between 

 the Ta3niopteroid ferns from Mesozoic and Palaeozoic rocks. 



It has been shown in a suggestive paper by White, 6 that we 

 have a number of Txniopteroid leaves, from rocks of different 

 ages, which may be safely placed in such genera as Danmtes 

 and others suggestive of botanic affinity ; but in the absence of 

 good evidence, either from fructification on the specimens them- 



1 PI. foss. Arct. vol. v. pi. iv. figs. 4-9. 



2 Trait, pal. veg. vol. i. p. 607. 



3 Vol. i. p. 133. 



4 Solras-Laubach, Fossil Botany, p. 136. 



6 Palseontographica, vol. xxxi. 1885, p. 169. 



6 Bull. Geol. Soc. America, vol. iv. 1893, p. 123. 



