NO. 1862. FOSSIL FERNS FROM THE POTOMAC GROUP— BERRY. 317 



Description. — Fronds large, bipinnate or tripinnate. Rachis very- 

 stout. Piiinse linear-lanceolate, becoming somewhat falcate in out- 

 line distad, and passing from alternate to subopposite. Pinnules 

 relatively wide, falcate, acuminate in the sterile forms but obtuse in 

 the fertile, variable in size according to their position. The distal pin- 

 nules which represent the reduced pinnee lower down on the frond 

 are larger and relatively more slender than the pinnules of the lateral 

 pinnae, which are almost as wide as they are long, and falcate. Be- 

 tween the two orders there is every gradation on each frond through 

 pinnatifid pumse to simple pinnule-hke forms. Margins entire or 

 sUghtly crenate, especially in the fertile pinnules, which are wider 

 than the sterile. Lateral veins usually but once forked, sometimes 

 simple. Texture coriaceous. Sori large, reniform in outHne, in three 

 or four pairs on either side of the midvein at the end of a distal branch 

 of a furcate vein. The structure or arrangement of the sporangia 

 can not be made out but the spores are preserved in abundance. 

 They are small, ranging from 0.083 mm to 0.05 mm in diameter, with 

 very thick walls, the outer surface covered with fine granulations not 

 visible with magnifications of 200 diameters or less. The tetrad scars 

 are very distinct. In form as well as size these spores are variable. 

 The smaller, possibly immature, spores are trigonal in outline, w^hile 

 the larger are more nearly spherical. 



This is a large and handsome species and is represented in the col- 

 lections by material of both the sterile and fertile fronds. It ranges 

 from the bottom to the top of the Potomac deposits, and outside the 

 Maryland-Virginia area is recorded from the Shasta beds of the Pacific 

 coast, the Kootenai of Montana, and the Lakota formation of the 

 Black Hills. There are a number of European Wealden species which 

 are similar to CladoiJhlebis jparva, but it is beheved to be quite dis- 

 tinct from its contemporaries, although small fragments of almost any 

 of the species of CladoplileMs are likely to be confused. 



Occurrence. — Patuxent formation : Fredericksburg, Cockpit Point, 

 Potomac Run, Virginia. Arundel formation: Ai'hngton (?), Mary- 

 land. Patapsco formation: Vinegar Hill, Maryland. 



Collections. — United States National Museum, Goucher College. 



CLADOPHLEBIS ROTUNDATA Fontaine, emended. 



Cladophlebis rotundata Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, p. 78, 

 pi. 20, figs. 9, 10.— (?) Penhallow, Summ. Geol. Surv. Can. 1904(1905), p. 

 9.— Fontaine, in Ward, Monogr. U. S. Geol. Surv., vol. 48, 1906, pp. 491, 510. 



Cladophlebis brevipennis Fontaine, Monogr. U. S. Geol. Surv., vol. 15, 1890, 

 p. 81, pi. 36, fig. 1. 



Description — In 1890 Fontaine describes this species as foUows: 



Frond bipinnate or tripinnate, arborescent(?); principal rachis stout, rounded, and 

 prominent; pinnae short, with a strong rigid rachis; ultimate pinnae, from the lower. 



