NO. 1862. FOSSIL FERNS FROM THE POTOMAC GROUP— BERRY. 327 



than ill the foreign material, and the rachis is inclined to be stouter and 

 may or may not be winged. 



This is an exceedingly common form in the Potomac from the oldest 

 to the youngest stratum and it has also been recorded from the 

 Kootenai of Montana at Great Falls, Geyser, etc., and possibly some 

 of Dawson's identifications of Asplenium dicksonianum Heer from the 

 Canadian Kootenai should also be referred to this species. It also 

 occurs in the Lakota formation of the Black Hdls, Abroad it is rather 

 rare in the English and German Wealden, but its geological distribu- 

 tion in the Lower Cretaceous of Portugal rivals that of eastern Amer- 

 ica since it comprises considerable material from the Valanginian, 

 Urgonian, and Albian terranes. With regard to its occurrence in the 

 Mesozoic of eastern Asia, Yokoyama writes^ that it is the ''chief 

 and characteristic fossil of the Japanese flora, being found in all of 

 the fossil localities." 



That this or OnycJiiopsis psilotoides, or both, occur in the Kome beds 

 of western Greenland seems probable, and several of Heer's species of 

 Asplenium, notably Asplenium dicksonianum Heer,^ suggest them- 

 selves for comparison. While the writer has not ventured to include 

 any of them in the synonymy of this species, they certainly are very 

 close to this type in appearance. The English occurrence of this 

 species is questioned in the foregoing synonymy since Professor 

 Seward ^ considers the Wealden material as identical with that of 

 OnycJiiopsis psilotoides. This may be true of the Wealden material 

 referred to, but it can hardly apply to that from America and Asia, as 

 the writer will show under the discussion of OnycJiiopsis psilotoides. 



Occurrence. — Patuxent fokmation: Fredericksburg, Trents Reach, 

 Cockpit Point, Dutch Gap, near Potomac Run, Colchester Road 

 (Pohick Creek?), Virginia; New Reservoir, Ivy City, District of 

 Columbia. Arundel formation: Langdon, District of Columbia, 

 Arlington(?), Maryland. Patapsco formation: Federal Hill (Balti- 

 more), Fort Foote, Vinegar Hill, Maryland; near Brooke, White 

 House Bluff, Mount Vernon, Chinkapin Hollow, Virginia. 



Oollections. — United States National Museum, Goucher College. 



ONYCfflOPSIS NERVOSA (Fontaine). 



Thyrsopteris nervosa Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 122, 

 pi. 25, figs. 4, 5, 16; pi. 37, figs. 2, 4; pi. 39, fig. 5; pi. 40, fig. 6.— Fontaine, 

 in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 511, 517, 519, 521, 528, 

 548, 571. 



Thyrsopteris meekiana Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 125, 

 pi. 38, figs. 2-4, 8; pi. 50, figs. 7, 8; pi. 51, fig. 3. — Fontaine, in Ward, IMonogr. 

 U. S. Geol. Sm-v., vol. 48, 1906, pp. 519,565; pi. 119, fig. 1. 



1 Yokoyama, Journ. Coll. Sci. Japan, vol. 3, 1890, p. 27. 



2 Flora foss. Arct., vol. 3, Abth. 2, 1874, p. 31, pi. 1, figs. 1-5; idem, vol. 6, Abth. 2, 1882, pp. 3, 33, pi. 2, 

 fig. 2; pi. 32, figs. 1-8. 



5 Seward, Ann. S. Afr. Mus., vol. 4, 1903, p. 7. 



