60 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



OSMUNDA, Liim. 

 O s in II n d a a f f i n ■ s , Lesqz. 



Plate IV, Fig. 1. 



Pteris affinis, Lesqx., Annual Report, 1873, p. 392. 



Frond simply pinnate; piunse subcoriaceous, abort, oblong-lanceolate, broader iu tbe middle, rap- 

 idly decreasing to an obtuse point, gradually narrowed downward, and apparently rounded to tbe point 

 of attacbment ; borders entire or irregularly undulate ; nervation thin but very distinct; lateral veins 

 open, dichotomous, generally forking twice, distant. 



The position of the pinnse (the midiUe one seemingly terminal), their 

 size and form, and also the characters of the nervation of this Fern seem to 

 indicate its generic relation with Osfnunda rather than with Pteris. The 

 pinnae oblong, enlarged in the middle, tapering to a point, about five centi- 

 meters long and two centimeters broad, probably represent the three upper 

 leaflets of a frond; this arrangement may be, however, casual, for the upper 

 pinna, which appears to be terminal, though somewhat larger than tlio others, 

 and of a different shape, has the midrib exactly of the same size. The 

 lateral veins, at an open angle of 50° about, slightly curve from their point 

 of attachment in passing to the borders, generally forking twice, and are very 

 distinct and distant, as in species of Osmunda. The rachis is not preserved. 



Recently, I have received from Rev. A. Lakes a splendid specimen, rep- 

 resenting jjart of a large pinna with four leaflets, a terminal one, the others 

 alternate, very oblique, joined to a broad rachis, which, in this specimen, as 

 in the one figured, is destroyed by maceration, its place being merely indi- 

 cated by the position of the leaflets. These are oblong-linear, four centi- 

 meters broad, at least sixteen centimeters long, judging from the preserved 

 part of one of the leaflets, which, broken apparently at the middle, measures 

 ten centimeters from the base. The nervation is of the same type as that of 

 the figure, the veins more generally forking quite near the base at the point 

 of attachment to the rachis. The substance is hard, rather coriaceous. 



The fragment described in Report, 1872, p. 376, as Pteris anceps appar- 

 ently refers to this species. 



Habitat. — Golden, Colorado ; not rare in fragments. 



