232 CORDAITEAE [CH. 



separated from one another by 2- 3 or it may be as many as 5 

 finer ribs or interstitial 'veins.' A statement by Weiss that in 

 Germar's type-specimen the longitudinal ribbing of the lamina 

 is very imperfectly preserved confirms the scepticism that is justly 

 felt as to the validity of this character as a satisfactory specific 

 criterion. 



The incomplete example shown in fig. 466, A, is 19-5 cm. 

 long and has a maximum breadth of 3-5 cm., but the complete 

 leaf was much larger and tapered gradually to the comparatively 

 broad and slightly concave or amplexicaul base. The narrow 

 elliptical proximal end of a specimen figured by Kidston 1 from 

 the Middle Coal Measures of Yorkshire is 2-8 cm. broad indicating 

 that the tangentially expanded leaf-scars on a branch recently 

 deprived of its foliage must have been a conspicuous feature. In 

 his synonymy of this species Kidston 2 includes Knorria taxina, 

 a species founded by Lindley and Hutton 3 on a piece of stem from 

 the Coal Measures of Newcastle. The type-specimen, as Mr 

 Howse 4 states, is much larger than the published drawing and 

 closely resembles in the decurrent leaf-bases with broad apices 

 the piece of stem represented in fig. 466, C, which Kidston identifies 

 as C. principalis. Geinitz 5 refers to this species the seeds named 

 Cordaicarpus Cordai (Gein.) ; but there is no evidence of connexion. 

 Kidston 6 points out that this seed is rare in Britain : he believes 

 that Cordaianthus Pitcairnae (Lind. and Hutt.) is probably the 

 inflorescence of C. principalis. 



Cordaites principalis occurs in both Carboniferous and Permian 

 strata. The leaves described by Lesquereux 7 from Pennsylvania 

 as C. Mansfieldi agree closely with C. principalis. Another 

 similar or possibly identical form is represented by C. Ottonis 

 Gein. 8 



1 Kidston (93) A. PL iv. fig. 16; (02) B. PI. LXIV. fig. 3. 



2 Kidston (93) A. p. 352. 3 Lindley and Hutton (33) A. PI. 95. 

 Howse (88) p. 112, fig. 7. 



Geinitz (55) A. p. 40, PL xxi. figs. 716. 

 Kidston (93) A. p. 355. 

 Lesquereux (80) A. p. 537, PL LXXVIIT. 

 Geinitz (62) p. 148, PL xxxv. 



