COAL ROCKS OF EASTERN VIRGINIA. 307 



width before it terminates. Our fossil thus agi-ees witli the 

 T. vittata in the elliptical outline of the upper half of the frond, 

 but differs from it in the undulating margin and more triangular 

 form of the part next the petiole. It is also wider in proportion 

 to its length. It is at once distinguished from the T. scitcmiinea, 

 which in other respects it very closely resembles, by the apex of 

 the latter liaving a reentering, cordate curvature. 



2d. The size of the frond. A comparison of the smaller and 

 more perfect fronds with fragments of the larger ones, often 

 amounting to one half or three fourths of the whole, has enabled 

 me to supply the outline of the deficient portions of many of the 

 latter, and has thus afforded data for measuring a number of the 

 fronds. The following are the dimensions of three, gi-eatly 

 differing in size : 



Inches. 



Frond A. Breadth, 2.4 



Estimated length by several fragments, . 14. 



Frond B. Breadth, ........ 4. 



Estimated length, ..... 24. 



Frond C. Breadth, . . . . ' . . . .6.4 

 Estimated length, . . . . .40. 



The breadths here recorded were all carefully measured upon 

 the specimens. The length of A, was deduced from the meas- 

 ured length of a fragment twelve inches long ; that of B, from a 

 fragment twenty inches long, and that of C, from several frag- 

 ments, from six to twelve inches long. The estimated lengths 

 of A and B, are probably a little less than the true lengths. 



3. The Midrib and Petiole. The Midrib is quite robust, hav- 

 ing, in some of the larger impressions, a width of from one third 

 to one half an inch, but gradually tapering towards the upper end, 

 it becomes extremely slender at the apex. On the upper side it 

 is marked by a somewhat deep groove and numerous parallel 

 striae. The Petiole is thick, rounded at the end, and about one 

 seventh the length of the frond. This slenderness of the midrib 

 towards the upper end, forms another feature of distinction be- 

 tween our fossil and the T. vittata, as figured by Brongniart, and 

 in this particular gives it more resemblance to the drawing given 

 by Lindley & Hutton of T. major. 



