<)24 MR A. C. SEWARD AND MR A. W. HILL ON THE 



some exceedingly well-preserved sections of L. fuliginosus, originally described by 

 Binney as Lepidodendron Harcourtii and as Halonia* 



There are no anatomical characteristics shown in the type - specimen of L. 

 Harcourtii nor in the larger stem from Airdrie,t which cannot be matched, more 

 or less exactly, in the Dalmeny and Arran species. This resemblance in structure 

 agrees also with the geological horizon from which the type-specimen of Witham 

 was obtained. 



We have no precise information as to the geological age of the larger stem of L. 

 Harcourtii described by Williamson from Airdrie ; the matrix in which the specimen 

 is embedded bears a close resemblance to that of the Dalmeny tree. There are, how- 

 ever, other examples | of what appears to be L. Harcourtii from the lower Coal- 

 measures of Lancashire and Yorkshire, but of the identity of these we do not wish to 

 speak with certainty at present. To be consistent with our belief of the specific 

 identity of Witham's type and the larger Airdrie stem with the Dalmeny stem, the 

 latter should be spoken of as L. Harcourtii (Witham). 



The conspicuous gaps accompanying the leaf-trace bundles, as seen in a transverse 

 section of the outer cortical regions of the stems of L. Harcourtii hitherto figured, are 

 not present in the large stem which we have described. The size of the parichnos, 

 part of which is shown in PL II. fig. 14 pr, agrees with the large dimensions of this 

 organ in the smaller specimens, and the absence of the gaps in the phelloderm-band in 

 the Dalmeny stem is in all probability due to the considerable development of phello- 

 derm, which compressed, and to a large extent obliterated, the parichnos tissue of the 

 leaf-traces which were no longer connected with leaves, as the older stems were leafless. 

 The slightly more prominent and obvious tooth-like projections of the corona in the 

 smaller stems may be accounted for by the presence of the broad zone of secondary 

 wood, but the long and narrow prominences shown in PL IV. figs. 24 and 34 are indeed 

 very similar to those of the smaller examples of L. Harcourtii. 



Williamson's nineteenth Memoir, the last of the splendid series which he com- 

 municated as sole author to the Royal Society, concludes with the paragraph : " We 

 have at least arrived at one result from the investigations recorded in the preceding 

 pages ; we now know that L. Harcourtii was not a distinct form, teaching an inde- 

 pendent and special philosophy. So far as its history is now known, it is substantially 

 identical with that of the other known Lepidodendra, teaching the same truths, and 

 leading to the same inferences. We only want, in my opinion, to discover it in its 

 arborescent condition to place it side by side with L. Wilnschianum as a true typical 

 exogenous Lycopod, and with which it has several external close relationships." § 



In the Dalmeny stem, and in the much less perfect stems from Arran, we have most 

 probably this " arborescent " form which Williamson refers to. 



* Binney (72). [Vide also Seward (99).] 



+ Section No. 380 (received by Prof. Williamson from the late Prof. Balfour of Edinburgh). 



% Specimens No. 1596A, 380B, etc., in the Williamson Collection [vide Williamson (93), pi. i.]. 



jj Williamson (93), p. 29. 



