DESCRIPTION OF TIIH SPECIES. 129 



alternate, liuenr, iicuto, narrowed to a lony, slender, wedge-shaped base, and 

 attacluid by th(! nudnorvo alone; [)innules cut more or less deeply and 

 obliquely into oblong or narrowly ovate, acute, diverging te«^tli ; niidnerve 

 slender; lateral nerves simple, one in each lobe or tooth, slender. 



Locality: Frederickshnrg ; rare. 



This plant belongs to the Sphnioptrris ManlcUi typo, and is strikingly 

 like 7'. iiislf/i/is. Tlie rachis, however, is not winged, and the pinnules are 

 narrowed to a Ioniser and more slender base. Tiiis jdant is not unconnnon 

 at Fredericks] lurg, and is sometimes found with piniudes even more slender 

 than those depicted. They cover with a confused heap some fragments of 

 the rock. 



Thyksopteris hensifolia, sp. nov. 



Plato XXXIX, Fis. :!; I'lal.' XL, Fi^'s. -2-5; Plate LI, Fi^. .^ 



Frond tripinnate, arI)oresc,ent ; leaf-substanco thick and coriaceous; 

 principal rachis strong, keeled on the under side ; })inn;v of ultimate order 

 alternate, short, linear-lanceolate, acute; pinnules crowded, obliquely 

 placed, short, subacute to obtuse, much narrowed at l)ase, and decurrcnt 

 in the basal ones to form a partial wing, those higher up united more and 

 more, and })assing through entii'e i)innules into more or less united lobes: 

 lower or basal pinnules cut very oblitpiely more or less deeply into sul)- 

 acute to obtuse teeth ; nerves very slender and seen with difiiculty, com- 

 posed in the pinnules of a inidnerve which sends off obliquel}' and alter- 

 nately into the teeth lateral nerves, which are once or twice forked and 

 curve outward. 



Localities : Fredericksburg ; T2d mile-post, near Brooke ; not un- 

 connnon. 



This plant is near Thyrsopterls i)isi{/nis, but the pinnules do not form 

 a continuous wing^ and the}' are, as a rule, shorter and broader than those 

 of the latter. The piiuuiles are more crowded, and the nerves differ much. 

 This plant has some resemblance to the Wealden fossil Sphenopteris 

 Ga'pperti Uindcer. 



MON XV 9 



