XVl] 



SIGILLARIA 



199 



gonal bases, while in other forms each leaf was seated on a 

 more or less prominent cushion having the form illustrated by 

 Sigillaria McMuHriei (fig. 194) or by the example represented in 

 fig. 200, H ; or as in the ribbed species shown in figs. 193, B, and 



Flo. 194. Sigillaria McMurtriei Kidst. From a specimen from tbe Upper Coal- 

 Measnres of Eadstock, in the British Museum (V. 952). Nat. size. 



195, the leaves in vertical series were separated from one another 

 by longer portions of the ribs. As in Lepidodendron the cushions 

 are frequently characterised by irregular transverse wrinklings 

 and other^ surface-ornamentation which in some instances at 



Fig. 195. Sigillaria mammillaris. (Khytidolepis form.) From a specimen in 

 the Manchester Museum. ^, parichnos; I, ligule-pit; t, loaf-trace ; 

 c, cushion ; s, leaf-scar. 



least may have been produced as the result of post-mortem 

 shrinkage of superficial tissue. From the rarity of shoots with 

 the foliage attached, it would seem that the leaves persisted for 

 a comparatively short time and were cut off by an absciss-layer 

 leaving behind a well-marked leaf-scar area. The linear leaves, 



' For an account of the various external features made use of in the classi- 

 fication of Sigillarias, see Koebne (0-1). 



