﻿90 PEOF. A. C. SEWARD OX [Feb. 1908, 



The stem sho"wn in the iigure has a diameter of 1*4 centimetres ; 

 the longest leaf measures 8 centimetres and is 1-4 cm. broad. A 

 comparison of this specimen with the figures given by Feistmantel 

 of fScJi. ffondu'anensis'^ from the Talchir, Damuda, and Panchet 

 Series of India leads one to suggest a possible identity ; the resem- 

 blance is very close, and there can be little doubt as to the relation- 

 ship, if not identity, of the African and Indian plants. 



FILICALES. 



Having regard to the recent demonstration of the impossibility 

 of identifying ferns by the characters of sterile leaves or even by 

 means of fertile specimens which do not exhibit reproductive organs 

 in a good state of preservation, it is with considerable hesitation 

 that such a genus as Thinnfeldia is included in the Filicales. 



Genus Thinnfeldia." 



Attention has elsewhere been called to the close resemblance 

 between plants described under the names Thinnfeldia, Ptilozamites, 

 Ctenopteris, Cycadojjteris, Lomatopteris ; I have suggested that the 

 use of different names has led to an exaggeration of slight differences 

 which are in many cases of little importance.^ Ettingshausen's 

 genus Thinnfeldia, as represented by the type-species Th. rhom- 

 hoidalis and by the southern type TTi. odontopteroides (Morr.), is 

 characterized by short and broad pinnules borne on long linear 

 pinnae as well as directly on the rachis of bipinnate fronds, and by 

 the apparent dichotomy of the frond-axis (PI. lY, fig. 1). The 

 venation exhibits considerable variation ; it is described as being 

 like that of Alethopteris, but ^^•ith a less-developed midrib ; or, 

 if a median vein is not present, it is characterized by the secondary 

 veins being given off from a common vascular branch from the 

 pinna-axis.^ Neither definition adequately describes the venation 

 of Thinnfeldia-i^ijiTLules. In the segments of Th. rhomhoidalis and 

 of T7i. odontopteroides there may be a distinct midrib, from which 

 forked lateral branches arise at an acute angle ; but in pinnules of 

 the latter species a midrib is frequently absent, and when this is the 

 case the veins by no means always arise from one common vascular 

 strand. In the pinnule represented in text-fig. 3 B (p. 91), some of 

 the veins are clearly branches of the axis of the pinna, while the 

 greater number are branches from a common strand. In the 

 ultimate segment shown in text-fig. 3 A, the veins appear to be all 

 independent and given off direct from the axis of the pinna. We 

 may describe the pinnules of Th. odontopteroides (to deal with one 

 species for the sake of clearness) as possessing a midrib which dies 

 out towards the apex of the lamina, and gives off either simple or 



1 Feistmantel (79) pi. i. figs. 2 & 3. - Ettingsbausen (52) p. 2. 



^ Seward (03) pp. 51-52 ; (04) pp. 174-75 & figs. 28-29 (pi. xvii). 

 •• Zeiller (00) p. 97 ; Potonie (99) p. 14S. 



