XI] SPHENOPHYLLUM PLURIFOLIATUM. 397 



were formed at different levels, thus producing a scaly type of 

 bark, such as we find in the Pine or the Plane tree. 



Before describing the structure of the strobili of Sphmo- 

 phyllum, we may briefly point out the distinguishing features of 

 two specific types of the genus recently described by Williamson 

 and Scott. One of these species, 8. insigne, was originally 

 described by Williamson as an Asterophyllites ; the numerous 

 narrow linear leaves in each verticil led to the inclusion of the 

 specimens in the latter genus. The material on which this 

 species is founded is from the volcanic beds of Pettycur, 

 Burntisland, on the coast of the Firth of Forth. 



1. Sphenophyllum insigne (Will.). Figs. 105, G and E, and 

 107, E and F. • 



1891 Asterophyllites insignis, Williamson i. 



An intercellular space occurs at each angle of the three- 

 rayed primary xylem strand, and spiral tracheae are abundant. 

 The tracheae of the secondary wood have scalariform markings 

 on the radial walls. Regular medullary rays extend through 

 the secondary wood. The phloem contains large sieve-tubes. 



This species occurs in the Calciferous sandstone rocks of 

 Burntisland, and has lately been recorded from Germany. It 

 characterises a lower horizon than S. plurifoliatum (Will, and 

 Scott). 



2. Sphenophyllum plurifoliatum (Williamson and Scott)^ 

 Figs. 105, A, B, and D, and 106. 



1891. Asterophyllites sphenophylloides. Will. ^ 



The specific name plurifoliatum was proposed by Williamson 

 and Scott for a type of stem originally described by Williamson" 

 as an Asterophyllites, from the Coal-Measures of Oldham, Lan- 

 cashire. This form of stem has not so far been connected 

 with any of the older species founded on external characters, 



1 Williamson (91), p. 13. ^ Williamson and Scott (94), p. 920. 



» Williamson (91), p. 12. ^ Ibid. (74). 



