500 Systematic Paleontology 



anastomose with branches sent off from other nerves of like grade higher 

 up to form very long, irregularly shaped, and lax meshes; ultimate 

 reticulation oblong, subrhombic, of quite uniform dimensions. This 

 genus is named for Prof. W. B. Rogers, who first called attention to 

 the plants of the Potomac formation and studied its geology.^' — 

 Fontaine, 1890. 



What has been said in the case of Protecephyllum and Ficophyllum 

 applies equally well to the present genus, which may be angiospermous, 

 but is more likely referable to the Gnetales, a problem which cannot be 

 solved until fruiting or structural material is discovered. 



EoGEESiA LONGiroLiA Fontaine 



Rogersia longifoUa Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 

 p. 287, pi. cxxxix, fig. 6; pi. cxliv, fig. 2; pi. cl, fig. 1; pi. clix, figs. 1, 2. 



Sapindopsis elliptica Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 

 p. 297, pi. cxlvii, fig. 3 (non Font, 1906). 



Rogersia longifoUa Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv., vol. 

 xlviii, 1905, p. 538 (non pp. 511, 523, pi. cxii, fig. 9). 



Description. — " Leaves narrowly elliptical, gradually narrowed to the 

 base and apes, with wedge-shaped base, acute, very long in proportion 

 to width; midrib comparatively very stout; primary nerves very slender, 

 going off very obliquely, proceeding upwards for some distance nearly 

 parallel with the margin, but gradually approaching it; primary nerves 

 sending off very obliquely secondary nerves, which anastomose with their 

 neighbors to form elongate, subrhombic, and irregular meshes, which 

 have their maximum dimensions turned upwards and slightly outwards; 

 primary meshes filled with pretty sharply defined ultimate meshes, 

 polygonal in shape, and varying in the number of sides from four to six.'^ 

 —Fontaine, 1890. 



No new facts regarding these peculiar forms have been obtained. 



Occurrence. — Patuxent Formation. Fredericksburg, near Dutch. 

 Gap, Kankeys, Virginia. Arundel Formation, Arlington (?), Mary- 

 land. 



Collection. — U. S. National Museum. 



