NO. 1862. FOSSIL FERNS FROM THE POTOMAC GROUP— BERRY. 321 



Description. — Frond large, bi- or tripinnate. Rachis stout and 

 rigid. Ultimate pinnae long, rather remote, alternate to subopposite. 

 Pinnules ovate to lanceolate and subfalcate in outline, sometimes 

 obtusely pointed mostly separate to the base, attached by their whole 

 base which is more or less widened. Venation of the type usual in this 

 genus. Margms usually entire, sometimes crenulate to subdentate 

 becoming entire distad. Texture coriaceous. The degree of sepa- 

 rateness of the puinules as well as their relative length and breadth 

 and their more or less falcate form are characters dependent upon the 

 age of the frond or the position of the pinnules on the frond, long 

 narrow almost straight proximal pinnules passing gradually into 

 more or less short, broad and falcate distal pinnules. 



This species is not very different from the widespread type of 

 CladopMehis commonly referred to the species alhertsii of Brongniart. 

 It exhibits considerable variation from specimen to specimen, but 

 these variations show so many gradations and are so readily explained 

 when the position of the various fossil fragments upon the frond is 

 taken into consideration that any segregation of them is entirely 

 unwarranted. In general the pinnules are larger and relatively 

 much wider than in CladopMehis alhertsii. 



The present species is very common at certain localities both in the 

 Patuxent and Arundel formations, and although it apparently sur- 

 vives during the deposition of the Patapsco formation it is less com- 

 mon. Outside of the Maryland- Virginia area remains of this species 

 have been reported from the Shasta beds of California and from the 

 Kootenai of Montana and British Columbia. Seward ^ refers the 

 bulk of Fontaine's figures of CladopMehis virginiensis Fontaine to 

 Todites williamsoni (Brongniart), a widespread older Jurassic species, 

 but this reference has no justification. CladopMehis nathorsti Yoko- 

 yama - from the Neocomian of Japan is very close to the present 

 Potomac species. 



Occurrence. — Patuxent formation: Fredericksburg, Dutch Gap, 

 Potomac Run, Virginia. Arundel formation: Arlington, Maryland. 

 Patapsco formation: Vinegar Hill, Maryland; Chinkapin Hollow, 

 Virginia. 



Collections. — United States National Museum, Goucher College. 



THE GENUS ONYCHIOPSIS. 



Yokoyama characterized the genus Onychiopsis as follows : " Fertile 

 segments different from the sterile. Sori terminal, linear, on each 

 side of the midrib, parallel with the margin, involucrate ; the involu- 

 crum of each side confluent over the midrib." ^ It was based on a 



1 Seward, Fossil Plants, vol. 2, 1910, p. 340. 



2 Yokoyama, Journ. Coll. Sci. Japan, vol. 7, 1895, p. 220, pi. 28, figs. 3, 4, 10, 11. 



3 Idem., vol. 3, 1890, p. 26. 



94428°— Proc.N.M.vol.41— 11 21 



