or little-known Fossil Lycopods. 359 



From the epidermal ornamentation of the cushions it is 

 also clear that the leaf was not attached to any part of its 

 surface, but to the vascular scar alone. 



This last character is of itself sufficient to exclude the plant 

 from Lep telodendron and restrict its relationship to Lepidophloios 

 or Sigillaria; but, as already indicated, the vascular cicatricules 

 are Sigillarian, and not those of Lepidophloios, and, in fact, 

 there is here only a Clathrarian Sigillaria with highly deve- 

 loped leaf-cushions. 



Of the three figures which I give of this plant figs. 3 and 5 

 must be regarded as representing the typical form. 



On all the specimens the leaf-scar is of the same shape, 

 but the slight sinus in its upper margin is sometimes very 

 feebly developed. 



In fig. 3 the ornamentation is more strongly marked on 

 the portion of the leaf-cushion below the leaf-scar than on 

 the part above it ; in fig. 5 the ornamentation covers more 

 equally the whole surface of the cushion. 



In fig. 4, on the other hand, the ornamentation is very 

 slightly represented ; so little is it shown that it can scarcely 

 be said to be present. Although on this specimen the leaf- 

 scars are larger and their cushions more elevated than in 

 figs. 3 and 5 (see fig. 4 a), it probably represents a younger 

 state of the plant, which, when older, would have the cushions 

 more drawn out, as in fig. 5. 



As figs. 3, 4, and 5 are drawn of the natural size, it is scarcely 

 necessary to give the measurements of the leaf-scars and their 

 cushions; these also vary considerably with the age of the 

 specimen. In all cases the leaf-scar is broader than high. 



In the decorticated condition the surface of the stem is 

 roughened by an irregular small mesh-like granulation, 

 which is more or less arranged in vertical lines (fig. 5, part 

 marked a). 



The only species to which Sigillaria McMurtriei has any 

 resemblance is Sigillaria tumida, Bunbury, sp. (Lepidoden- 

 dron? twnidum, Quart. Journ. Geol. Soc. vol. iii. p. 432, 

 pi. xxiv. fig. 1). From this species it differs in the form of 

 its leaf-cushions. The surface-ornamentation in Sigillaria 

 tumida also differs in being " rather irregular, wavy, longitu- 

 dinal strise." 



Bunbury described his plant as Lepidodendron ? tumidum. 

 and Schimper places it in Lepidophloios * ; but I believe that 

 this plant is also a Sigillaria. 



In his description Bunbury does not mention the form of 



* Schimper, Traite d. paleout. v6g6t. vol. ii. p. 52. 



25* 



