DESCRIPTION OF THE SPECIES. 123 



ThYRSOPTERIS RARINERVIS, sp. IIOV. 



Plate XXVI, Kiss. 0, 7; Plate XLIII. I'igs. 4-6; Plate XLIV, Figs. 1. 2, 5; Plato XLIX, Fig. -i: Pl.-ite 



CLXIX. Figs. <;. 7. 



Frond tri[)iiinate, arborescent ; jjrinciijal racliis and tliat of tlie pcmil- 

 tiniate piinia' .strong, rigid, straight: that of the ultimate pimia' ratlier 

 slender; pemiltiinate and ultimate })inna' alternate: ultimate piiimi' more 

 or less distinctly petioled, linear-lanceolate, acute; pinnules diminishing 

 in size from the base to the tips of the ultimate piinue, pa.ssing from 

 toothed pinnules separate nearly to the base, through entire pinnules more 

 fully united, to lobes at the summit of the piniuv ; pinnules line;ir to 

 narrowly elliptical, acute, oblitpiely jjlaced, decurrent, and united at base 

 to form a wing of vai-ying width, thick and leathery, narrowed at base, 

 those of the lower portion of the fniiul and of the pinna- minutely dentate; 

 towards the sunnnit of the compound pinn;e the ultimate pinna; reduced 

 to lobed and toothed pinnules ; nerves of the i)iunules of the normal kind, 

 composed of a distinct miduerve, which sends off alternately into each lobe 

 or tooth a single nerve. 



Localities: Fredericksbin-g: 7 2d mile-post, near Brooke ; White House 

 Bluff; entrance to Trent's Beach. 



This fine |)lant is pretty widely distributed, and at White House Bluff 

 it is by far the most common fern. The forms depicted in PI. CLXIX, 

 Figs. G, 7, come from this place, and are plainly but small portions of 

 what were once large fragments. The plant is not common at the entrance 

 to Trent's Beach. PI. XLIV, Fig. 2, give.s, slightly restored, a fine speci- 

 men found here. Fig. 1 of the same plate, and PI. XLIX, Fig. 2, give 

 two very good specimens which come from Fredericksburg. The first 

 named seems to be the upper part of the compound pinna depicted in the 

 last-named figure. The principal rachis seems to have been keeled or 

 ridged on the under side. 



This plant is one of the Sphcnoptcris 3Ia»feUi type, and perhaps by 

 some would be united with that species, but it is more robust, and the 

 pinnules are more like those of the Thyrsopteris type. ' It looks in some 

 points a good deal like Sphenopfcris loufiifolia, Dunker (Mon. Weald., PI VIII, 

 Fig. 4), which Schenk unites with «S'. (iocpperti. It however differs from S. 



