154 Mr. A. C. Seward on 



In 1864 Coemans and Kickx published a monograph 1 

 on this genus, and their definition, like Brongniart's, makes 

 the wedge-shaped form of the leaves and the absence of a 

 median nerve essential characters. Every observer recog- 

 nises the great diversity of form which exists in Spheno- 

 phyllum leaves, but whether Asteropliyllites may be con- 

 sidered an extreme case of this variation in leaf-form is 

 a matter of dispute. Prof. Williamson has more than once 

 expressed his belief that Asteropliyllites and Sphenophyllum 

 cannot be regarded as distinct genera. He says 2 : " Astero- 

 pliyllites and Sphenophyllum are genera so closely allied 

 that their separate existence finds but little justification 

 in nature." Professors Solms-Laubach, Renault, and others 

 maintain that these two genera are clearly defined and 

 cannot but be considered as distinct. Prof. Weiss, 3 without 

 going so far as Carruthers and Stur in regarding Astero- 

 pliyllites and Sphenophyllum as branches of Catamites, 

 admits that it is impossible to attach any great importance 

 to the difference in leaf-form as a means of distinction 

 between these two genera. 



The figures given by Schenk 4 and Germar 5 (reproduced 

 in Figs. 2 and 3) shew better than any I know the associa- 

 tion of the wedge-shaped type of Sphenophyllum leaves with 

 others much narrower and more deeply dissected. That in 

 these cases we have true Asterophyllitean leaves, that is 



1 Monographic des Sphenophyllum d'Europe ; par MM. Coemans et Kickx. 

 Bull, de VAcad. Royale de Belgique. 33 me annee, 2 me ser. Tab. xviii. p. 134. 

 (1864). 



- On the organisation of the Fossil plants of the Coal- Measures. Pt. IX. 

 Phil. Trans. Royal Society. Pt. II. 1878, p. 334. 



3 Neues Jahrbuch fur Mineralogie, Geologie und Palaontologie. 1879, 

 p. 262. 



4 Richthofen. China, Bd. IV. Pflanzl. Versteinerungen v. Schenk. 

 Taf. xliv., Fig. 1. 



6 Die Versteinerungen des Steinkohlengebirges von Wettin und Lobejun 

 im Saalkreise. Taf. VI., Fig. 3. 



