XVIIl] OMPHALOPHLOIOS 265 



characterised by clearly defined rhomboidal areas or cushions (fig. 

 217, E) like those oi Lepidodendron, except in the absence of a 

 median keel, and similar to those on some forms of Sigillaria 

 Brardi. A short distance above the centre of each cushion is 

 an oval or subcordate region bounded by a rim-like margin and 

 containing a small oval scar, presumably that of a vascular strand. 

 A triangular elevation which also shows a small pit (Fig. 217, 

 E, a) occurs below the oval area. The appearance of the 

 surface-features varies considerably on different parts of a single 

 specimen. Fig. 217, D, represents one of the numerous figures 

 published by White in his detailed account of the American 

 material. Each cushion bears a widely open V-shaped ridge, 

 which is described as a leaf-scar ; above this is an oval area (2*5 



—a, 



Fig. 217. Omphalophloios. 

 D. After White. E. After Kidston. 



mm. X 1'75 mm.), the surface of which is bounded by a narrow 

 rim. Within the rim is a smaller concave oval region with a 

 small pit near its upper end. 



We cannot, in the absence of petrified material, arrive at 

 any satisfactory conclusion as to the meaning of these surface- 

 features. White considers that Omphalophloios is probably a 

 rhizome of one of the arborescent Lycopods, but whether or 

 not this is its true nature must be left for future discoveries. 

 The fact that the rootlet bundles of some Stigmarian axes are 

 accompanied by a parichnos strand, as Weiss has shown, may 

 prepare us for the discovery of surface-features on Stigmariae 

 not unlike those of Omphalophloios. (Fig. 193, C.) 



A possible comparison may be suggested also with Sigillaria 

 Brardi as figured by Germar (fig. 196, A) in which circular 

 scars, which may be the scars of rootlets, occur below the leaf- 



