DESCRIPTION OF THE SPECIES. 261 



CXXVI, Fig. (J, PI. CXXVIII, Fig. 1, and VI CLXVII, Fig. 2, the loaves 

 are shorter, more couve.x, and more closely appressed than in others. 

 Indeed, there is a considerable degree of variation in the leaves. In such 

 forms as PI. CLXVII, Fig. 2, the leaves are thick, horny, and exceedingly 

 durable. They can be detached from the shale in the form of small black 

 shining scales. 



In this and other forms of Sphenolepidhm the facial leaves often appear 

 of somewhat different shape from the lateral ones, being more obtuse, prob- 

 ably from their close appression to the stem. I'he forms, such as PI. 

 CXXVIII, Fig. 1, resemble Ettingshausen's Widdrinntonitcs IlaidnKjeri 

 from the Wealden of Hanover (see Beitriige zur Flor. der Wealdenperiode, 

 PI. XI, Fig. 1). 



This plant is the most common conifer at the 72d mile-post, a place 

 where conifers form the predominant fossils. It is a widely diffused species. 



Sphenolepidium Sterni5Ergianum (Dunk, sp.) Heer. 



Plate CXXI, Figs. 8, 10, 11 ; Plate CX.KX, Fig. 9. 



Branches .slender, long, remote, going off very oblifpiely ; leaves linear, 

 falcate, acute to acuminate, sometimes acicular, patent, dijcurrent, inuch 

 wider at base, with slender but distinct midnerve, apparently disticlious, 

 and attached only laterally ; cones not seen. 



Localities : llill-side near Potomac Run ; Fredericksburg. 



This, the normal form of S. Sternhoyjicuium, is comparatively rare, 

 being much less common than the variety dcitsifoliam. It differs from 

 Heer's forms onh- in not showing leaves on the U[)per surfaces of the twigs, 

 but this is no doubt due to the removal of these leaves from their more 

 exposed position. 



Sphenolepidium Sternbergianum, var. densifolium Ileer, sp. 



Plato CXVIII, Fig. 7; Plato CXXI, Figs, .'i, 7, 9; Plato CXXV, Fig. 2; Plato CXXIX, Fig. 3; 

 Plato C'XXX, Fi-. 1; Plato CXXXI, Figs. 1, I! ; Plato CXXXIl, Fig. 4. 



Branches slender, ultimate twigs going off ver}' obliquely so as to 

 appear dichotomoiis, tending to a fastigiate arrangement, subdividing irreg- 

 ularly ; leaves short, lateral ones acute, linear to narrowly ovate, diverg- 



