DESCltlPTiO>I OF TUE SrEClES. 139 



Localities: Fredericksburg; fisliing-lmt above Dutch Gap Canal; 

 rare. 



Plate LIV, Fig-. ], depicting a specimen from the last-mentioned local- 

 ity, differs from the more common Fredericksburg forms in having tlic 

 penultimate rachis keeled, perliaps because the under side is shown. It 

 gives the summit of a primary pinna. 



This pretty little fern seems to form a well-marked new species. 



TlIYRSOPTERIS HETEROLOBA, sp. nOV. 

 Plate LIII, Fig. 4. 



Frond trij)innate; rachises strongly winged; principal racliis flex- 

 uous; penultimate ])innii' alternate, with a strong rigid rachis; ultimate pin- 

 na- alternate, short, attached by the narrowly winged rachis which forms a 

 sort of petiole, cut obliquely into oblong, obtuse, or spatulate piniudes or 

 lobes to varying depth, according to the position on tlie pinuiX' ; upper 

 basal pinnules alwa3-s larger than the lower pinnules, furnislied witli three 

 shallow, very obtuse lobes ; towards the sunmiit of the ultimate jjinna- and 

 of the frond the pinnules pass to obtuse lobes; nerves in eacli pinnule and 

 lobe fine, closely placed, flabellately diverging, with simple or forking 

 branches. 



Locality : Fredericksburg ; rare. 



This seems to be a very distinct new species, and it is very rare. It 

 is somewhat like T. varians. 



Thyrsopteris BELLA, sp. nov. 



Plate LIII, Fig. 5; Plate LV, Figs. G, 7; Plato LVI, Figs. 2. 5; Plate LVII, Figs. 1, 5; Plato LVIII, 



Fig. 4. 



Frond quadripinnate, spreading, arborescent ! ; rachises comparatively 

 very slender; primary rachis somewhat flexuous; penultimate pinnae 

 alternate or opposite, long, closely placed, passing towards the summit of 

 the principal pinna; into ultimate pinnae ; ultimate pinna? short, opposite 

 to alternate, terminating in a three-lobed segment, usually closely jjlaced, 

 oblong-lanceolate in form, passing above into lobed and simple pinnules ; 

 pinnules passing in ascending into simple ones, and finally into lobes, 



