38 PTERIDOSPERMEAB [CH 



with convex areas 13 cm. long. A similar cast, 36 cm. broad, 

 has recently been figured by Nathorst^ from the Culm of Spitz- 

 bergen, and from the Upper Devonian of EUesmere Land the 

 same author has described impressions of a cortical reticulum 

 under the name Lyginodendron Sverdrupi^. These specimens are 

 interesting as pointing to the former occurrence in the Arctic 

 regions of stems — probably Lepidodendroid — reaching the dimen- 

 sions of a fairly large tree. As Potonie* pointed out, Gourlie's 

 generic name serves a useful purpose for casts of stems of the 

 type shown in fig. 401 that cannot be assigned to a definite 

 systematic position. The genus was first used for a specimen 

 which has nothing to do with the plant usually spoken of as 

 Lyginodendron oldhamium (Binney). Though loath to give up 

 a name by which Binney's type has long been known, in spite of 

 its retention in the second volume of this work I feel compelled 

 so far to conform to the recognised principles governing nomen- 

 clature as to adopt Potonie's generic term Lyginopteris. 



Lyginopteris oldhamia (Binney). 

 i. Stem. 

 1866. Dadoocylon oldhamium, Binney, Proc. Lit. Phil. Manchester, vol. v. 



p. 113. 

 1869. Dictyoxylon oldhamium, Williamson, Monthly Micros. Journ. vol. n. 

 p. 66. 



1873. Lyginodendron oldhamium, Williamson, Phil. Trans. Roy. Soc. vol. 



CLXTTT. p. 404. 

 1899. Lyginopteris oldhamia, Potoni6, Lehrbuoh der Pflanzenpalaeontologie, 

 p. 171. 



ii. Leaf. 

 1828. Sphenopteris Hoeninghansi, Brongniart, Prodrome, p. 51. 

 1872. Edraxylon, Williamson, Proc. R. Soc. vol. xx. p. 438. 



1874. Eachiopteris aspera, Williamson, Phil. Trans. R. Soc. vol. clxiv. p. 684. 

 1877. Calymmatotheca Hoeninghausi, Stur, Cuhn Mora, n. p. 266. 



1905. Crossotheca Hoeninghausi, Kidston, Proc. R. Soc. vol. Lxxvi. p. 358. 



iii. Seed. 

 1877. Lagenostoma, WiUiamson, Phil. Trans. R. Soc. vol. CLXvn. p. 234. 

 1903. Lagenostoma Lomaxi, Ohver and Scott, Proc. R. Soc. vol. lxxi. p. 477. 



iv. Root. 

 1876. Kaloxylon Hookeri, Williamson, Phil. Trans. R. Soc. vol. clxvi. p. 23. 

 1 Nathorst (14) PI. vn. fig. 1. ^ Nathorst (04) B. p. 11. s Potonie (99) B. p. 171. 



