50 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



their base like the pinnules, and these are cut in more or less deep lobes, also 

 of the same pointed form. The mode of division of the secondary pinnse is 

 seen in fig. 1 a. These are larger toward the base of the frond, and their 

 pinnules are pinnately, acutely lobed; farther up, the pinnae are simply lobed, 

 like the pinnules. This fine Fern has also an evident relation to Aspknivm 

 Wegmanni, Brgt., of the Sezanne Flora, by Saporta, p. 317, pi. 2, figs. 2 and 3; 

 a species described also by Watelet in the Flore Foss. du Bassin de Paris, an 

 Eocene formation like Suzanne. 



Habitat. — Golden, Colorado, where it is often found, but rarely in frag- 

 ments as large as the specimen figured and communicated by Rev. Arthur 

 Lakes, of the School of Mines of Colorado. 



Splieiiopteris membranacca, Lesqz. 

 Plate II, Figa. 2, 2 a, 3, 3 a. 

 Sphenopieris memhranacea, Lesqx., Annual Report, 1873, p. 394. 



Frond bi-tripiunate ; primary pinnas long, linear-lanceolate, rigid, erect or at an acute angle of 

 divergence from the main rachis ; pinnules narrow, linear-lanceolate, connected near the rachis by the 

 decurrent base, pinnately 5-6-lobed ; lobes short, slightly obtuse, distinct, single-nerved. 



This form has nearly the same characters as the preceding, and may be 

 a variety of it. Its facies is, however, very different, as seen from its mem- 

 branaceous shining substance, its rigid divisions, the narrower pinnules, all 

 separated to near the base, by which they are decurrent along the rachis, and 

 generally close to it, forming a narrow border. The slightly obtuse lobes and 

 the narrow pinnules give to this Fern a likeness still more marked to that of 

 the Mount Promina flora. It seems, however, to differ hy its membranaceous 

 substance, and by the veinlets, always simple, while they are described by 

 d'Ettingshausen as forking in his species. The affinity is, however, evidently 

 very close. Fig. 2 a is from a fragment representing the same species, with 

 pinnules less deeply divided, and which seems intermediate between both 

 forms. The substance is also shining and membranaceous. A small frag- 

 ment, represented in figs. 3 and 3 a, has been merely mentioned in Rep., 

 1869, p. 196, under the name of Lustrea arguta?, with the remark that it 

 might be a Pecopteris. It is evidently referable to this or the former species. 



Habitat. — Grolden, same locality as the former. The last fragment was 

 in the first lot of specimens sent to me from the collection of Dr. J. L. Le Conte, 

 of Philadelphia. The other specimens have been obtained by Rev. A. hakes. 



