42 



M, YO KO Y AM A. 



Leaf elongated, entire or rarely segmented, parallel-sided, rounded at 

 apex ; veins very fine, dense, perpendicular to the rhachis. 



This species at first sight reminds us of the genus Taenioptcris 

 among ferns, but U decidedly different from that genus in having the 

 blade of the segments inserted on, and not laterally to, the rhachis. 

 The leaf seems to have been in most cases entire, with sides strictly 

 parallel except near the apex, where it is sometimes seen slightly to 

 taper (fig. 11). Fig. 12 shows such a parallel-sided leaf. It is 58 mm. 

 long and about 12 1 / 2 mm. broad without any appreciable difference 

 in breadth in its upper and lower extremities. Fig. 14 shows a nar- 

 rower leaf which measures 9 mm. in breadth. But that the leaves 

 were not always entire is shown by fig. 2 b, which represents one side 

 of a leaf divided into rectangular segments about 8 mm. broad. The 

 veins are very fine and dense, about four to the millimetre. They 

 are very faint, and almost obliterated in fig. 11, but are distinct in 

 fig. 13 and 14. 



Leaves are in most cases strongly convex on their upper surface 

 along the rhachis, but concave on both sides of it, as is seen in 

 fig. 13 and 14. 



This species is allied to the preceding in having very dense veins 

 and generally entire leaves, but is distinguished in having the former 

 strictly at right angles to the rhar-his and the latter narrower and 

 more elongated. 



Fragments are frequent at Ozo. 



26. Nilssonia nipponensis m. 

 PI. VI, fig. 8d. H. VII, fig. 2-7, 8a. PI. XII, fig. 6. 

 PI. XIII, fig. 1. 

 Leaf petioled, segmented, incisions sharp ; segments opposite or alter- 

 na 'e. acute, more or less concave in the upper margin, con rex in the lower, 



