306 ON THE AGE OF THE 



layer adjoining this impression upon the surface of the slate, 

 and the number of such impressions found in the layers of a 

 fragment of the roc^k only one or two inches thick, imply that the 

 hollow stem of the plant which produced them, was extremely 

 thin, and easily compressed. Whether it was of the same genus 

 with the plants whose fossil relics have been arranged under the 

 title of calamites, it would be impossible as yet to determine. As 

 far as may be inferred from external appearances, it would seem 

 to be referable to that group. Hanking it, therefore, for the 

 present, with the long list of doubtful fossils included under this 

 generic head, I propose the specific name of planicostatns, as 

 descriptive of the remarkable flatness of its ribs. 



T.ENIOPTERIS MAGXIFOLIA. 



The impressions of this superb plant are found in great num- 

 bers in some of the dark gray slaty layers and feiTuginous bands 

 above the coal, and even upon the surfaces or partings of certain 

 varieties of the coal itself. This fossil retains so perfectly the deli- 

 cate markings of the original frond, that I have been able to 

 compare it satisfactorily with the other species of the same genus, 

 figured and described by Brongniart, Phillips, Lindley and Hut- 

 ton, and Sternberg, and have thence been led to consider it as a 

 new species. The particulars in which it differs from the Tcs- 

 niopteris vittata, Brongn. and T. scitaminea (Presl.) Sternberg, 

 the two species which it most nearly resembles, will appear from 

 the following description : 



1st. The form of the frond. Although among my specimens 

 there is no large frond, in which both the extremities are entire, 

 the nvimerous fragments of fronds, exhibiting the ends as well as 

 the middle portions of different leaves, enable me very satisfac- 

 torily to trace the figure of the frond, in an advanced stage of 

 growth. This may be described as oval-lanceolate, but with this 

 peculiarity, that while the upper or free end is formed by a grad- 

 ual curving of the margin, from the wide part of the frond toward 

 the end, so as to present a very regular and nearly elliptical 

 sweep, the lower extremity tapers towards the petiole, in a some- 

 what irregular and undulating manner, and is greatly reduced in 



