90 THE POTOMAC OR YOUNGER MBSOZOIC FLORA. 



posed of a midnerve, which sends off very obliquely alternate forked or 

 simple nerves that go into the lobes and teeth. In each segment there 

 are several nerves, which diverge flabellately into the teeth. 



Localities : Fredericksburg ; fishing hut above Dutch Gap Canal ; 

 rare. 



This small plant has a well-marked Sphenopteris facies. It is some- 

 thing like Sphenopteris Williamsonis Brongn. and also resembles somewhat 

 S. denticidata Brongn., of the Oolite of England, but seems to be distinct 

 from both of these and a well marked new species. 



Sphenopteeis acrodentata, sp. nov. 



Plate XXXIV, Fig. 4. 



Frond tripinnatifid ; secondary pinnjB opposite, very short, terminat- 

 ing in a round-lobed segment which is cuneate at base ; ultimate pinnpe or 

 pinnules subopposite, the lower ones cut obliquely in broadly elliptical 

 lobes or pinnules nearly down to the midrib, lobes and pinnules narrowed 

 towards their bases, the upper ones reduced to pinnules which are fir.st 

 lobed and then simple ; pinnules and lobes at their summits rounded, very 

 obtuse, and furnished with very minute teeth; nerves of the rounded lower 

 pinnules and of the lobes, several times forked and diverging flabellately, 

 the ultimate branches ending in the teeth. 



Localities : Fishing hut above Dutch Gap Canal ; Baltimore, on Cov- 

 ington street ; very rare at both localities. 



The specimens figured come from the Dutch Gap locality. Tiie plant 

 is more common here than at Baltimore. A small fragment only was 

 found at the latter place. 



Sphenopteris latiloba, sp. nov. 



Plato XXXV, Figs. 3-5 ; Plate XXXVI, Figs. 4-9 ; Plate XXXVII, Fig. 1. 



Frond tripinnate, arborescent; principal rachis ver}^ stout; leaf-sub- 

 stance thick and coriaceous ; primary pinnas opposite, and having a stout, 

 rigid rachis, which is often somewhat flexuous; ultimate pinnae remotely 

 placed, veiy short, passing towards the summit of the principal pinna or 

 of the frond through lobed pinnules into entire ones ; pinnules remotely 



