422 PSARONIEAE [<^H. 



Caulopteris peltigera has scars measuring 6 — 9 by 4 — 6 cm. ; 

 it occurs in the Commentry Coal-field of France in associa- 

 tion with the fronds known as Pecopteris cyathea, a species 

 which Kidston regards as identical with P. arborescens^. 



ii. Megaphyton. 



The first use of this name was by Artis^, who gave it to a long 

 flattened cast, Megaphyton frondosum, found in Carboniferous 

 strata in Yorkshire, characterised by two vertical rows of large 

 scars and by impressions of sinuous roots. Kidston records the 

 genus from the Middle and Upper Coal-Measures of Britain. 

 A good example of this type of cast is afforded by M. McLayi 

 Lesq.^ from the Coal-Measures of North America, which has 

 been recognised in European Carboniferous rocks. The leaf- 

 scars are rounded or oval, broader than high; the vascular 

 impression has the form of a closed ring (5 — 8 x 3 — 6 cm.), 

 more or less circular and with a tendency to a rectangular 

 outline, characterised by a deep inverted U-shaped sinus in the 

 middle of the lower surface and by a W-shaped impression 

 of an internal strand (fig. 298, B)^. 



iii. Ptychopteris. 



This generic name, instituted by Corda", is applied to 

 decorticated stems of Psaronius, the surface of which is that 

 of the vascular region on which the form of the leaf-scars is 

 more or less clearly defined. The scar-areas are limited by an 

 impression of the sclerenchymatous sheath enclosing the leaf- 

 meristele, and internal to this is the impression of the leaf-trace. 

 In some specimens a layer of coaly material which represents 

 the carbonised cortex and adventitious roots covers the Ptycho- 

 pteris cast. The Ptychopteris cast represented in fig. 299 

 shows the decorticated surface of part of a long stem on which 

 the leaf-scars are arranged as in Megaphyton. An example of 



1 Kidston (86) A. p. 113. = Artis (25) A. PI. xx. 



^ Lesquereux (66) A. 



* Renault and Zeiller (88) A. PL xl. ; Grand'Eury (90) A. 



» Corda (45) A. ; see also Grand'Eury (90) A. ; Renault and Zeiller (88) A. 



Pis. XXXVIII. — XL. 



