416 Proceedings of the Royal Physical Society. 



cushion ornamented with fine granulations placed in irregular 

 lines and more prominent on the lower part of the cushion. 

 Leaf-scar situated on the upward-directed elevated summit of 

 the cushion, elongated, rhomboidal ; lateral angles prominent 

 and produced, the lower angle rounded, the upper rounded, 

 with a slight sinus. Vascular cicatricules three, the two 

 lateral oval and directed outwards, the central transversely 

 linear and placed below the centre of the lateral cicatricules. 



Remarhs. — This species of Sigillaria in some of its char- 

 acters has a superficial resemblance to both Lepidodendron 

 and Lepidophloios. 



Figures 3 and 5 have very much the appearance as if the 

 leaf-scar were surrounded by a "field ^' as in Lepidodendron; 

 but the apparent "field" is merely a cortical extension, 

 similar to the leaf-cushions in the Clathrarian Sigillarim, and 

 only differing from the other members of this group of Sigil- 

 laria in its more highly developed condition. 



On the lower part of the cushion occurs a flattened area, 

 which runs from the lower rounded angle of the leaf-scar to 

 the base of the cushion. In the centre of this band is a very 

 gently raised line, from each side of which, at an almost 

 imperceptible angle, slope the two sides of this flattened area. 

 The surface of the cushion is ornamented with irregular 

 granulations, which appear to be roughly arranged in lines 

 springing from its base. 



The extent to which the cushions are elevated is shown in 

 the vertical sections. Figs. 3a, 4a, and 5a, which respectively 

 represent sections of cushions and leaf-scars from specimens 

 drawn at Figs. 3, 4, and 5. From the examination of this part 

 of the fossil it is evident that we are dealing with a cortical 

 extension similar to the leaf-cushions of the Clathrarian 

 Sigillarice, and not with the ''field" of a Lepidodendroid 

 leaf- scar. 



The much-elevated cushions in Sigillaria McMurtriei have 

 a considerable resemblance to those of Lepidophloios ; but 

 the character which at once proves this plant to be a true 

 Sigillaria, and not a Lepidophloios, is the form of the vascular 

 cicatricules. Of these the two lateral are linear-oval, the 

 central transversely elongated and placed below the centre of 



