246 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



grown so far apart. The leaves of the Potomac plant are apparently not 

 quite so thick as those from Kome and not so constantly incurved, and 

 they are usually more closely placed. The cones of the Potomac plant 

 have the free surface not so much elongated transversel)', and the transverse 

 depression on their sununit is greater. 



Sequoia rigida Heer. 



Plate CXVIII, Fig. 3; Plate CXXI, Fig. 2; Plate CXXVI, Fig. 2; Plate CXXX. Fig.:l. 



Leaves coriaceous, rigid, linear, acuminate at apex, patent, straight, 

 one-nerved, transversely very finely rugulose, not narrowed at base, 

 adnately long decurrent. 



This description of S. rigida, given by Heer,' agrees very well with 

 some of the Potomac conifers, the transverse rugosity alone being absent. 

 This, however, is accidental, and due to the accidents of preservation. The 

 localities for the Potomac fossils are near Telegraph Station ; hill-side near 

 Potomac Run. The form PI. CXXI, Fig. 2, is one of the most common 

 plants near Telegraph Station. Heer says that this species is more common 

 in the Atane than in the Kome beds. PI CXXX, Fig. 3, is a good deal like 

 Ghjptostrohus Grcenlandicus, as given by Pleer.^ He speaks of the leaves 

 of S. rigida as prolonged into a fine point. This feature may be seen on a 

 number of the specimens of the Potomac fossil. It is not, however, a 

 character that would in most cases be preserved. It is noteworthy that so 

 fiir as seen this species does not occur at Fredericksburg and Dutch Gap. 



Sequoia densifolia, sp. nov. 



Plate CXXI, Fig. 4. 



Stems slender; leaves narrowly linear, acute and acuminate, strongly 

 falcate, widest at base, decurrent and adnate, showing a tendency of the 

 leaves to crowding and aggregation into groups, in which the members have 

 their bases overlapping in some cases, or adnate; midnerve slender but 

 distinct. 



Localit}' : Fishing hut above Dutch G.np Canal; very rare. 



'Flor. Foss. Arctica, vol. 3, p. 80. ^ Flor. Foss. Arctica, vol. 3, PI. XXII, Fig. 12. 



