Maryland Geological Survey 259 



reniform in shape, and distributed in two rows, one on each side of the 

 midvein, attached to the summit of the upper branch of a furcate vein. 



This species is quite generally distributed throughout the Potomac 

 formations, although there is but one recorded occurrence from the 

 Arundel formation. It is abundant in the Patuxent formation at Fred- 

 ericksburg, and outside the Maryland- Virginia area it has been recorded 

 from the Kootanie formation of Montana and British Columbia and the 

 Shasta of the Pacific coast province. 



The sterile and fertile pinn^ are closely similar in outline and vena- 

 tion, the former being much more abundantly represented than the 

 latter. They are both very similar to those of Cl(idophlehis parva Fon- 

 taine, and may be compared with a number of European and Kome 

 species of Cladophlehis, Alethopteris, Pecopteris, etc. 



Occurrence. — Patuxent Formation. Fredericksburg, Dutch Gap, 

 Telegraph Station (Lorton), Virginia; Broad Creek, Maryland. Arun- 

 del Formation. Arlington, Maryland. Patapsco Formation. Chink- 

 apin Hollow, Virginia. 



Collection. — U. S. Nationq^l Museum. 



Genus DRYOPTERITES gen. nov. 

 The desirability of an additional form-genus for the reception of the 

 fossil remains of ferns which resemble those of the recent genus Dnj- 

 opteris of Adanson,^ but fail to furnish conclusive diagnostic characters, 

 is obvious. The probability of a large and dominant modern genus like 

 Dryopteris preserving its generic integrity when traced back to a time 

 as remote as the Lower Cretaceous is altogether unlikely and the number 

 of other modern genera with species whose foliar characters are similar 

 to some of the many modern species of Dryopteris is another reason for 

 abandoning the modern name for the I^ower Cretaceous forms, and a 

 third reason might be furnished by the action of the last International 

 Botanical Congress which decided to "conserve" the name Aspidium of 

 Swartz,^ although Adanson's name for these modern forms preceded it 

 by more than the span of a generation. 



^ Adanson, Fam. PI., vol. ii, 1763, p. 20. 



- Swartz. Schrad, Jour. Bot., vol. ii, 1800, p. 4. 



