Maryland Geological Survey 303 



tion on the frond, passing in ascending, in the upper part of the pinnae, 

 through toothed and undulate pinnules into entire ones; lower pinnules 

 attached by the rachis alone, and deeply cut into broadly ovate-obtuse 

 lobes; up higher in the pinnae, and on the frond they have ovate teeth 

 and are attached by the middle of the much-narrowed base, and are 

 slightly decurrent; towards the top the ultimate pinnse pass into cre- 

 nately lobed segments, and these into lobed and toothed pinnules, like 

 those lower down; all are acute; leaf-substance thick and leathery; mid- 

 nerve neuropteris-like, and vanishing before attaining the apex of the 

 pinnules; lateral nerves occur in the lower portions of the pinnules 

 mostly in nerve groups ; all go off very obliquely and fork usually several 

 times, very fine and closely placed, but distinct." — Fontaine, 1890. 



This species is the only one of this genus in the Potomac flora which 

 is reasonably well characterized. It has been recorded from the Patuxent 

 formation near Potomac Eun, Virginia, and from the Shasta beds of 

 California, but in both cases the identifications were erroneous, and it 

 appears to be confined to the Patapsco horizon where it is not common. 

 It resembles considerably in its general f acies the older Mesozoic species 

 of Thinnfeldia from Europe. 



Occurrence. — Patapsco Formation". Near Brooke (common). White 

 House Bluff (rare), Virginia; Ft. Foote (rare), Maryland. 



Collection. — TJ. S. National Museum. 



Thinnpeldia granulata Fontaine 

 Plate XL, Figs. 1, 2 



Thinnfeldia granulata Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 1889, 



p. Ill, pi. xxvi, figs. 10-12; pi. xxvii, figs. 1-5, 8; pi. clxix, fig. 1. 

 AcacicepJiyllum longifoUum Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 279, pi. cxxxvii, fig. 6; pi. cxxxviii, figs. 1-3. 

 Acacicfphyllum spatulatum Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 280, pL cxxxviii, figs. 4, 6-9. 

 Acacicephyllum microphyllum Fontaine, 1890, Mon. U. S. Geol. Surv., vol. 



XV, 1889, p. 280, pi. cxxxviii, fig. 5. 

 (?) Acacicephyllum variaMle Fontaine, 1890, Mon. U. S. Geol. Surv., voL 



XV, 1889, p. 281, pi. clxx, fig. 7. 

 20 



