DESCRIPTION OF THE SPECIES. 169 



These Platyptei'igia must liave attained a great size, rivaling- that of 

 Macrokeniopteris magnifolia of the Virginia Rha^tic. For some time, when 

 only very imperfect specimens had been found, I thought that these were 

 fissured leaves of that or a nearly allied plant. 



My recollection of the lost tip of the leaf in I'rofessor Uhler's collec- 

 tion is not definite enough to enable me to describe it accuratel}*, for I 

 examined it only casually, expecting to be able later to critically study it. 

 Tlie leaf tapered graihudly to a .sul)acute point, much as do some of those 

 of M. magnifolia. 



The larger specimens of this subgenus probably formed portions of 

 leaves that must have been over two feet long (60"") and a half foot wide 

 (15"™). The rachis is very stout and wide, with a ridge or cord running in 

 the middle on the lower side. The upper side is smooth, or with a maiginal 

 ridge on each side. Fragments of leaves 25"" long, and without sensible 

 diminution in their width, have been obtained, and some specimens 14''"' 

 wide were seen. Midribs with a width of 9""" have been found, and a por- 

 tion of a petiole showed the width of 13'""'. The nerves towards the base, 

 as shown in PI. XXXI, Fig. 2, are more oblique in their course than in the 

 middle of the leaf The ridge in the center of the midnerve on the under 

 side seems to be due to the woody l)un(llo of the true midnervo, sliowing 

 by pressure througli the thick epidermis. This epidermis on the midnerve 

 is striated parallel with the length of the leaf. None of the lateral nerves 

 are furcate even at base. 



Platyptekigium densinerve, sp. nov. 



Phito XXX. Fi^. •■^; I'latr XXXF, Fi^s. 1,4; Plato XXXII, Figs. 1, 2; Plato XXXIII, Fig. 1; Plate 

 XXXIV, Fig. 1 ; Plato XXXV, Figs. 1, 2. 



Leaves very large, probably GO''" and more in length, and as much as 

 20''"' ill width; leaf-siibstanco very thick and membranaceous; midnerve 

 moderatelv strong, covered with a thick, dense epidermis, which is striated 

 parallel with the length of the leaf, and which makes the midnerve appear 

 wider than it really is, on the lower surface sometimes appearing ridged 

 in the middle, on the u[)per.side smooth or corded on each margin at the 

 attachment of the lamina of the leaf; laminae entire, or more commonly cut 



