Maryland Geological Survey 461 



Occurrence. — Patapsco Formation. Ft. Foote, Prince George's 

 County, near Wellhams, Anne Arundel County, Maryland; Mt. Vernon, 

 Virginia. 



Collection. — TJ. S. National Museum. 



PopuLOPHYLLUM RENiFORME Fontaine 

 Plate LX'XXI, Figs. 3-6 



Populophyllum reniforme Fontaine, 1890, Mon. U. S. Geol. Survey, vol. xv, 



1889, p. 311, pi. civ, fig. 9; pi. clvi, fig. 3. 

 Populophyllum hederwforme Fontaine, 1890, Mon. U. S. Geol. Surv., vol. xv, 



1889, p. 311, pi. clxvi, fig. 3. 

 Protecephyllum reniforme Ward, 1895, 15th Ann. Rept. U. S. Geol. Survey, 



p. 360, pi. iv, figs. 5, 6 (non Font). 

 Populophyllum menispermoides Ward, 1906, in Fontaine, Mon. U. S. Geol. 



Survey, vol. xlviii, 1905, p. 498, pi. ex, figs. 3, 4 (non fig. 2 which is 



Populus potomacensis Ward). 



Description. — Leaves of small or medium size, orbicular or reniform 

 in outline, 3 em. to 7 cm. in length by 3 cm. to 7 cm. in greatest width 

 which is about half way between the apex and the base. Margin entire 

 or slightly undulate. Petiole very stout, of considerable length. Vena- 

 tion palmate, camptodrome. Primaries 4 to 7 from the top of the petiole, 

 usually 7 in number, very fine in calibre and often invisible, the midrib 

 slightly more prominent than the lateral primaries; these soon fork 

 and anastomose in broad arches sending off branches which form similar 

 secondary and tertiary arches. Basal sinus shallow with the basal auricles 

 of the leaf lamina uniformly rounded, ranging to forms in which the 

 sinus is narrow and as much as 2 cm. deep with the auricles of the 

 lamina somewhat angular. 



This curious species is especially common, although usually in a 

 fragmentary condition, in the Patapsco beds in the vicinity of Aquia 

 Creek, Virginia. It is scarcely related to Populus and by its thick 

 petiole and fine venation is suggestive of an aquatic plant. Mention 

 has already been made {supra) of its resemblance to some of the forms 

 referred to the genus Chondrophyllum but this gives no better clue to 

 its botanical affinity. In Portugal Saporta has described similar remains 

 from the Albian beds of Buarcos under the names Menisper mites cerci- 



