134 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



Thyksopteris distans, sp. nov. 



Plate XLVII, Fig. :! ; Plate LIV, Fig. 8. 



Frond tripinnate, large, arborescent ; rachises strong, narrowly winged; 

 pinna; and pinnules very remotely placed ; penultimate piniuG subopposite, 

 with ultimate pinna? abruptly and irregularly diminished in length and 

 size ; ultimate pinna; linear-lanceolate, passing above into lobed, toothed, 

 or entire pinnules ; basal pinnules of the lowermost ultimate pinna; nar- 

 rowly oblong, acute, denticulate, passing towards the tips of the ultimate 

 pinnse rapidly into narrowly oblong, acute lobes and teeth; nerves in the 

 pinnules and lobes, composed of a midnerve which sends off obliquely 

 and alternately on each side brandies, which are forked in the lower ones, 

 simple above, fine, closely placed, but distinct. 



Locality : 72d mile-post, near Brooke ; not uncommon. 

 * This plant belongs to the Splienopteris Gcepperti type. The principal 

 rachis is very strong. It is probable that in this and all the specimens of 

 Thyrsoptcris, CJadophlebis, Pecopteris, etc., the principal rachises are portions 

 simply of compound pinnie. In the descriptions, when plants are given as 

 bipinnate, tripinnate, etc., it is meant that the frond is probably at least 

 divided to the extent named. This plant seems to be not very near any 

 other described fossil. 



Thyrsoptebis angustiloba, sp. nov. 



Plate XLVIII, Figs. 3-5; Plate LV, Fig. 3. 



Frond tripinnate; rachises distinctly winged; pinnules and lobes, 

 especially the latter, very narrow ; penultimate pinnag alternate, rapidly 

 diminished in ascending towards the summit of the compound pinnae into 

 ultimate pinna3 and pinnules, and finally into lobes ; ultimate pinnas sub- 

 opposite, closely placed, decurrent to form a wing, the lower ones cut 

 obliquely and more or less deeply into narrowly oblong or elliptical 

 pinnules towards their bases, but towards their ends these pass into lobes 

 and teeth of the same form, narrowed to a subpetiolate base ; higher on 

 the compound pinna they change rapidly through toothed pinnules into 



