DESCRIPTION OF SPECIES. 23 



Plate VI, Fig. 1, represents, apparently, a portion towards the summit 

 of a frond. Plate V, Fig. 5, gives a fragment of a larger frond, on which 

 the margins are wanting. The character of the lateral nerves on this spec- 

 imen on the right-hand side, seems to be the normal one, that is, they are 

 slightly oblique. On Plate VI, Figs. 1, 2, they are at right angles to the 

 middle nerve and margin. In Plate VI, Fig. 2, we have enough of the 

 frond preserved to give us the width of one of the plants of large size. 

 The width of this specimen was at least 17 centimeters, and the frond must 

 have in all its dimensions rivaled the largest of the specimens of M . magni- 

 folia. It will be noted that the margin of the specimens given in Plate VI, 

 Figs. 1, 2, is represented as having a thickened and rigid border. This is 

 true of M. magnifolia also, but the thickened margin is in that plant less 

 obvious than in M. crassinervis. This character of the margin enables us 

 easily to determine when the lamina is entire, and when apparent undula- 

 tions are due simply to laceration. 



I have identified this plant, without hesitation, with Feistmantel's plant 

 found at Murero and Buskoghat, in the Rajmahal Group of India. 

 Feistmantel says, however, that his plant is not large. The representation 

 given of it in "Pal. Ind.,'' series ii, 7, on plate xxviii, in figs. 1, 2, 3, 

 2 a, 2b, clearly shows that the specimens were fragmentary, and did not 

 give the entire width of the frond. The undulation of the margin noted 

 by Feistmantel is evidently due to the laceration of the margin. These 

 figures show plainly that the India plant is the same with that from 

 Virginia. 



This species is one of the most clearly defined of all the forms of Ma- 

 crotseniopteris. Its strongly prominent and rigid midrib is not much flat- 

 tened, and is sharply distinct from the lamina of the frond on each side. 

 The lateral nerves are very distinct, and stand out like threads, even on 

 sandstone, the only rock which contains it. The plant is very rare. I have 

 never seen any specimens anywhere except at Clover Hill, and here it occurs 

 only with a few fragments in a rather siliceous sandstone under the main 

 seam. It is associated in this sandstone with plants found as yet only here. 



Formation and locality. — Clover Hill, in sandstone under the main coal, 

 and between it and the bottom seam. 



