408 Mr Wills, Notes on the genus ScMzoneura, 



Having now examined what is known of the plant originally 

 described as ScMzoneura, let lis turn to a consideration of the 

 other species, with the special object of seeing whether the genus 

 is homogenetic. 



Names have been given to seven species ranging in age from 

 the Permo-Carboniferous to the Rhaetic, while several other 

 fragments of stems have been referred to the genus. The follow- 

 ing table gives the distribution in time and space and the chief 

 characteristics of the various named species. 



One or two notes are necessary relative to the table. In 

 the first place it will be observed that the description of the 

 nervation of both S. africana and S. gondwanensis differs from 

 the usually accepted one which states that stout median nerves 

 are present. I have, however, examined undoubted specimens of 

 S. gondwanensis at the South Kensington Museum, on some of 

 which, e.g. No. V, 7099, several distinct fine parallel nerves can 

 be seen. 



The original specimen also of S. africana (Asterophyllites of 

 Hooker*) in the Museum of the Geological Society likewise shows 

 some three distinct nerves down the centre of some of the leaves. 

 I use the term leaf here, not as Seward has done in redescribing 

 S. africana f, where he applies the word to what I would call a 

 sheath-segment, but in the same sense as Schimper and Feist- 

 mantel. 



In the second place, little is known of S. wardi, and the 

 description given by Zeiller leaves some doubt as to its nature. 

 It seems, however, possible that the nervation is multiple. 



Let us now refer to the table. It is evident at once that 

 Halle is well justified in classing 8. carrerei, 8. hoerensis and 

 8. meriani together, and the institution of the genus Neocalamites 

 appears expedient. The type of plant represented by 8chizoneura 

 (Neocalamites) carrerei seems to have been almost world-wide in 

 distribution in Rhaetic times ; so far so, in fact, that the Euro- 

 pean, Asiatic and African species are almost indistinguishable. 



Of the remaining species, 8. wardi, although but imperfectly 

 known, appears to have approximated to the Neocalamites type : 

 yet it may have possessed multiple nervation. In this case, as 

 it is likely that the nervation is a generic quality, it could not 

 be easily classed with that group but would fall in more naturally 

 with the remaining species. 



These three, 8. paradoxa, 8. africana and *Si. gondwanensis, 

 agree closely with one another in the possession of a multiple 

 nervation, in the small number of leaves, and in the usual union 



* Bain, A. G., " On the Geology of Southern Africa," Trans. Geol. Soc. Ser. 2, 

 Vol. vii. 1845-56 (1852), p. 175. 

 t Seward, A. C., loc. cit. p. 89. 



