326 PROCEEDINGS OF THE NATIONAL MVSEVM. vol.41. 



Thyrsopteris demrrens Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 130, 

 pi, 43, fig. 7; pi. 46, figs. 2, 4; pi. 49, figs. 5-7.— Fontaine, in Ward, Monogr. 

 U. S. Geol. Surv., vol. 48, 1906, pp. 484, 491, 511, 525, pi. Ill, fig. 11. 



Thyrsopteris virginica Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 120, 

 pi. 24, fig. 1. 



Thyrsopteris pachyrachis Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 

 132, pi. 46, figs. 3, 5; pi. 47, figs. 1, 2; pi. 49, fig. 1.— Fontaine, in Ward, 

 Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 487, 538, 557. 



Thyrsopteris elliptica Fontaine, Monogr. U. S. Geol. Svu-v., vol. 15, 1890, p. 133, 

 pi. 24, fig. 3; pi. 46, fig. 1; pi. 50, figs. 6, 9; pi. 51, figs. 4, 6, 7; pi. 54, fig. 6; 

 pi. 55, fig. 4; pi. 56, figs. 6, 7; pi. 57, fig. 6; pi. 58, fig. 2.— Fontaine, in Ward, 

 19th Ann. Kept. U. S. Geol. Surv., pt. 3, 1898, p. 482; pt. 2, 1898, p. 482.— 

 Fontaine, in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 290, 484, 

 514,517, 528, 557, pi. 71, figs. 12, 13.— Knowlton, Smiths. Misc. Coll., vol. 4, 

 pt. 1, 1907, p. 110. 



Thyrsopteris distans Fontaine, Monogr. IT. S. Geol. Surv., vol. 15, 1890, p. 134, 

 pi. 47, fig. 3; pi. 54, fig. 8. 



Thyrsopteris pinnatifida^o-titA.m'E, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 136, 

 pi. 51, fig. 2; pi. 54, figs. 4, 5, 7; pi. 57, fig. 7.— Fontaine, in Ward, 19th 

 Ann. Kept. U. S. Geol. Surv., pt. 2, 1890, p. 658, pi. 161, figs. 1, 2.— Fontaine, 

 in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, p. 511. 



Thyrsopteris varians Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 137, 

 pi. 52, figs. 2^; pi. 53, figs. 1-3; pi. 54, fig. 10; pi. 57, fig. 2. 



Thyrsopteris 7-hombifolia Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 138, 

 pi. 52, fig. 5; pi. 54, fig. 1. 



Thyrsopteris bclla Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 139, pi. 53, 

 fig. 5; pi. 55, figs. 6, 7; pi. 56, figs. 2, 5; pi. 57, figs. 1, 5; pi. 58, fig. 4.— Fon- 

 taine, in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 491, 511. 



Thyrsopteris microloba Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 140, 

 ■ pi. 57, fig. 4. 



Thyrsopteris microloba alata Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, 

 p. 140, pi. 55, fig. 5; pi. 58, fig. 1. — Fontaine, in Ward, Monogr. U. S. Geol. 

 Surv., vol. 48, 1906, p. 281. 



Thyrsopteris insequipinnata Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, 

 p. 142, pi. 57, figs. 3, 8. 



Thyrsopteris rhombiJoba Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 144, 

 pi. 89, fig. 7; pi. 60, fig. 8. 



Description. — Yokoyama, in 1890, described this species as follows: 



Frond slender, bi-tripinnated ; sterile pinnae alternate or rarely opposite, elongated, 

 their length rapidly increasing toward the lower part of the frond; pinnules alternate, 

 acutely directed forward, lanceolate or linearly lanceolate, entire or lobed, or even 

 pinnately parted; lobes or partitions acute at apex and acutely directed forward 

 just like the pinnules themselves. Venation obsolete, secondary veins simple, each 

 going into a lobe. Fertile pinnules elongated, with a linear terminal sorus on both 

 sides of the midrib . 



A very large number of Fontaine's species of Thyrsopteris fall within 

 the limits of this species. There is, to be sure, some variation in the 

 relative length and breadth of the pinnules, but the material shows 

 every gradation of form, it being possible to select individual pinnules 

 from a single frond fragment which exemplify several of the su]i- 

 posed types. On the whole the pinnules are somewhat more robust 



