NO. 1862. FOSSIL FERNS FROM THE POTOMAC GROUP— BERRY. 315 



Description. — Frond large, bipinnate or tripinnate. Principal 

 rachis rather slender. Pinnae remote, shortening rapidly distad. 

 Proximad they are pinnatifid, changing first into pinnules with 

 undulate margins and then into those with entire margins in passing 

 toward the apex of the frond. Pinnules elliptical in outline, con- 

 stricted at the base, which is rounded or subauriculate. Venation of 

 the usual Cladoplilebis type. 



This species has been identified at a number of localities in Mary- 

 land and Virginia, but it is not common at any of these. Outside 

 this area it has been reported from the Kootenai of Montana, and 

 very similar forms occur in the Kome beds of Greenland, as, for 

 example, those which Heer described as Pecopteris arctica,^ Pecop- 

 teris andersoniana,^ and Pecopteris liyperborea.^ Abroad the species 

 described by Schenk * from the German Wealden as Alethopteris 

 cycadina is very close to the American species, as Fontaine has 

 already pointed out. 



Cladoplilebis constricta exhibits considerable variation in the degree 

 of remoteness and outline of the pinnules, and may possibly include 

 more than one species, the fact that certain of these aberrant forms 

 come from the low horizon at Fredericksburg while all of the other 

 occurrences are from Patapsco outcrops lends some credence to this 

 suggestion. The species has been reported by Penhallow from the 

 Kootenai in Canada, but this determination can not be accepted with 

 certainty. 



Occurrence. — Patuxent formation : Fredericksburg, Virginia. Pa- 

 tapsco formation: Hell Hole (?), Brooke, Deep Bottom, Virginia; 

 Federal Hill (Baltimore), Vinegar Hill, Fort Foote (?), Maryland. 



Collections. — United States National Museum. 



CLADOPHLEBIS DISTANS Fontaine, emended. 



Cladophlebis distans Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 77, 

 pi. 13, figs. 4, 5. — Fontaine, in Ward, Monogr. U. S. Geol. Surv., vol. 48, 

 1906, pp. 280, 572. 



Dryopteris frederichshurgensis Knowlton, Bull. 152, U. S. Geol. Surv., 1898, 

 p. 92.— Fontaine, in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 280, 

 512, 538, 548, pi. 112, fig. 2. 



Aspidium frederichsburgense Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, 

 p. 94, pi. 11, figs. 1-6; pi. 12, figs. 1-6; pL 16, fig. 9; pi. 19, figs. 6, 7.— Pen- 

 hallow, Trans. Roy. Soc. Can., sec. 3, vol. 1; sec. iv, 1908, p. 307. 



Description. — Frond large and coarse, - bipinnate or tripinnate. 

 Rachis very stout and rigid. Pinnse of the ultimate order mostly 

 alternate, rarely opposite or subopposite, with rigid and proportion- 

 ally rather slender rachises, very long, linear. Pinnules alternate, 



1 Heer, Flora foss. Arct., vol. 1, 1868, p. 80, pi. 1, fig. 13; pi. 43, fig. 5. 



2 Idem., vol. 3, Abth. 2, 1874, p. 41, pi. 3, flg. 76. 

 ' Idem., vol. 1, 1868, p. 81, pi. 44, fig. 4. 



< Palaeont., vol. 19, 1871, p. 218, pi. 31, flg. 2. 



