290 MESOZOIC FLORAS OF FXITED STATES. 



niidril) and sui)p()rio(l on sliort l;unina> that are so nnich modified that 

 they are redmcd lo thickened veins. This form, in the hirge sori and 

 short .stout pecUcels carrying them, is even more hke Heer's Dicksonia 

 claripes than the fertile forms of I), niontanensis. PI. LXXI, Fig. 8, 

 gives a portion of this magnified to show the sori, which, belonging 

 to a Dieksonia, ha\-e their valves closed and showing their outer sur- 

 face. I'l. LXXI, rig. 0, represents a somewhat different fragment of 

 a fertile pinnule, which has also large sori on short stipports. But 

 these latter are more foliaceous than those shown in Fig. 7, and have 

 on each side of the nerve which bears the sori at its sununit a whig 

 formed by a remnant of the lamina of the pinnule, giving a form appar- 

 ently not so much altered from the sterile pinnule as is that figured 

 in Fig. 7. This wing, however, is thickened and gives with the sorus 

 a club-shaped or spatulate form. Fig. 10 gives a portion of this mag- 

 nified. Fig. 11 represents the small specimen collected by Mr. AYeed 

 at the Gilt Edge coal mine in the Judith Mountains, about 50 miles 

 east of the place where most of the other specimens were obtained. Its 

 chief importance is due to the fact that it was upon this specimen that 

 the author founded the species. 



The plant occurs in both Professor Ward's and Mr. Weed's 



collections. 



Genus THYRSOPTERIS Kuntze. 



TlIYRSOPTERIS ELLIPTICA Foiltallie. 



PI. LXXI, Figs. 12, 13. 



1889. TTiyrsopteris eUiptica Font.: Potomac Flora (ilonogr. U. S. Gcol. Surv., 



Vol. XV), p. 133, pi. xxiv, figs. 3, 3a; pi. xlvi, figs. l,«la; pi. 1, figs. 6, 6a, 9; 



pi. li, figs. 4, 6a, 61); pi. liv, fig. 6; pi. Iv, fig. 4; pi. Ivi, figs. 6, 6a, 7; pi. Ivii, 



figs. 6, 6a; pi. Iviii, figs. 2, 2a. 

 1898. TTiyrsopteris eUiptica Font.? in Weed & Pirsson: Eighteenth Ann. Rep. U. S. 



Geol. Surv., 1896-97, Pt. Ill, p. 482. (PI. LXXI, Fig. 13.) 



Two specimens of a fern apparently identical with Thyrsopteris 

 eUiptica, a characterisic plant of the Lower Potomac of Virginia, were 

 found, one by Mr. Weed at the Grafton locality and the other by Pro- 

 fessor Ward near Geyser. The latter is figured in PI. LXXI, Fig. 12, 

 and the former in Fig. 13. They are fragments of ultimate pinna^, 

 but contain pinnules sufficiently well preserved to leave little doubt 

 that they belong to the Potomac plant. 



