258 Systematic Paleontology 



in uniting under a single specific name fern fronds from all quarters of 

 the globe which closely resemble each other, and probably future study 

 will show that even the present treatment is faulty in this particular. 



Occurrence. — Patuxent Formation. Woodbridge, Fredericksburg, 

 Dutch Gap, Telegraph Station (Lorton), Virginia. Patapsco Forma- 

 tion. Chinkapin Hollow, Virginia. 



Collection. — U. S. National Museum. 



Cladophlebis distans Fontaine 

 Plate XXXII, Figs. 5, 6 



CladophleMs distans Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 



p. 77, pi. xiii, figs. 4, 5. 

 Aspidium fredericksMirgense Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 94, pi. xi, figs. 1-6; pi. xii, figs. 1-6; pi. xvi, fig. 9; pi. xix, 



figs. 6, 7. 

 Dryopteris fredericJcsJ)urgensis Knowlton, 1898, Bull. U. S. Geol. Surv., 



No. 152, p. 92. 

 CladophleMs distans Fontaine, 1906, in Ward, Mon. U. S. Geol. Surv., vol. 



xlviii, 1905, pp. 280, 572. 

 Dryopteris frederickslturgensis Fontaine, 1906, in Ward, Mon. U. S. Geol. 



Surv., vol. xlviii, 1905, pp. 280, 512, 538, 548, pi. cxii, fig. 2. 

 Aspidium fredericksburgense Penhallow, 1908, Trans. Roy. Soc, Can. (iii), 



vol. i, sec. iv, p. 307. 

 CladophleMs distans Berry, 1911, Proc. U. S. Natl. Mus., vol. xli, p. 315. 



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

 chis very stout and rigid. Pinnse of the ultimate order mostly alternate, 

 rarely opposite or subopposite, with rigid and proportionally rather slen- 

 der rachises, very long, linear. Pinnules alternate, oblong or ovate, ob- 

 tuse, slightly falcate, and usually with a somewhat rounded and slightly 

 constricted base, separate, more or less remote, in some specimens those 

 of the lower pinn^ with crenate margins, those of the upper ones entire, 

 passing in the middle part of the frond through pinnules with undulate 

 margins. Leaf-substance thick and leathery. Midvein of the usual 

 CladopMebis type, that is, strong at base and dissolving into branches 

 at the summit; lateral veins of the crenate and undulate pinnules in 

 groups in each tooth, composed of a midvein which sends off alternate 

 simple branches, or else of forked veins with one of the branches forking 

 again; those of the pinnules with entire margins usually once forked, 

 all quite distinct; fertile specimens rare. Sori very large, elliptical or 



