MARYLAND GEOLOGICAL SURVEY 765 



The Long Island and Marthas Vineyard forms have these sori in a single 

 row on each side of an axis, and some of the South Carolina specimens 

 seem to have a similar arrangement, while others have them definitely in 

 threes, one terminal and two lateral. This latter arrangement also pre- 

 vails exclusively in the Greenland specimen and in similar material from 

 the Magothy formation of Maryland. This variation is of minor impor- 

 tance and is mentioned simply because it is believed that the grouping 

 in threes is the normal arrangement, which has been obscured during fos- 

 silization in the instances where it is not clear. 



As here understood this species ranges from the Atane beds of Green- 

 land southward in the Magothy formation of Marthas Vineyard, Long 

 Island and Maryland, to the Middendorf beds in South Carolina. 



Occurrence. MAGOTHY FORMATION. Eound Bay, Maryland. 



Collection. U. S. National Museum. 



Genus CLADOPHLEB1S Brongniart 

 [Tableau, 1849, p. 25] 



This genus, which is essentially a form-genus, is usually restricted to 

 certain fern-remains of Mesozoic age, a number of which are certainly 

 to be referred to the family Polypodiaceae. Cladophlebis has been fully 

 discussed by the writer * in a recent volume of this series and need not be 

 recharacterized in the present connection. It is a waning and unimpor- 

 tant type in Upper Cretaceous floras everywhere, a fact due in all proba- 

 bility to generic evolution and consequent modernization of the Upper 

 Cretaceous Polypodiaceae. 



CLADOPHLEBIS SOOIALIS (Heer) Berry 



Pecopteris socialis Heer, 1882, Fl. Fossils Arct, Bd. vi, Ab. ii, p. 34, pi. vii, 



fig. 4; pi. viii, fig. 15; pi. xxxiii, fig. 9 (non Fontaine, 1890). 

 Cladophlebis socialis Berry, 1911, Bull. Torrey Bot. Club, vol. xxxviii, p. 409. 



Description. " P. foliis bipinnatis, pinnis oppositis, elongatis, lanceo- 

 lato-linearibus, inferioribus pinnatifidis, lobis, subtriangularibus, inte- 



1 Berry, Md. Geol. Survey, Lower Cret, 1911, pp. 239-259. 



