308 ON THE AGE OF THE 



4. The Nervures. As in the T. vittata, T. scitaminea, and a few 

 other species, the nervures of our fossil are nearly or exactly at 

 right angles to the midiib. They are, however, far more delicate 

 and numerous than in T. vittata. Moreover, after a careful ex- 

 amination of the nervures of more than twenty fragments, I have 

 been unable to discover more than three or four instances of 

 their bifurcation, cither near the mickib, or at any other part of 

 their length ; while, on many large and distinct specimens, not a 

 single example of bifurcation could be found. Simplicitij of the 

 nervures is, thercjforc, to be ranked as one of the characters of 

 our fossil. In the T. vittata, on the other hand, according to 

 Brongniart, " the nervures are sometimes simple, sometimes 

 bifurcated either towards the base, the middle, or near the extrem- 

 ity ; " and in Brongniart's figure, the bifurcated nervures are as 

 numerous as the simple ones, the two being aiTanged alternately. 

 In Sternberg's definition of the species, a similar frequency of 

 bifurcation is implied by the words " venis horizontalihus fur- 

 catis, cum simplicihus alternantibns." ■ 



5. The position and size of the supposed points of fructification. 

 On many of the fronds of the Virginia fossil an iri'cgular row of 

 circular depressions is seen, on each side of the midrib, and not 

 unfrequently on the midrib itself. These hoUows would seem, 

 as in the vittata, to mark (according to Brongniart) the position 

 of the roundish groups of capsules. They are, however, much 

 larger than in that species, being from one sixth to one fourth of 

 an inch in diameter, and are placed at unequal intervals asunder, 

 and at rather varying distances from the midrib. 



The peculiarities above described, especially the form and 

 size of the frond, and the almost invariable singleness of tlie 

 nervures, would seem to furnish ample reasons for regarding the 

 Virginia fossil as distinct from either the T. vittata or T. scitaminea, 

 although nearly allied to both. Looking upon it as forming a 

 new species, I have ventured to give it the title of T. mag-nifolia. 



T. magnifolia. Frond, varying from one to six inches in 

 width, and from seven to forty inches in length, curving ellipti- 

 cally towards apex, tapering with an undulating margin towards 

 base, supported by a thick petiole about one seventh the length of 



