jnowltox.i DESCRIPTION OF SPECIES. 25 
Branches regularly, pinuately arranged at right angles to the main 
:achis; leaves (!) close, two ranked, deeply laciniate; lacuna* linear, 
slightly intlated toward the point, either simple from the base or 
lichotomous. 
The type specimens of this species, as well as many better- preserved 
mes, are in the United States National Museum collection. The species 
vas well described by Lesquereux, except that the recent specimens 
;how it to have been pinnate. 
The generic reference of this fossil is by no means satisfactory. It 
tppears to have been a weak plant, probably growing in or near water, 
bod this is a suggestion that it belongs to the alga?. In order to obtain 
he opinion of an authority on alga 1 , specimens and drawings were 
ent to Mr. F. S. Collins, of Maiden, Massachusetts, the well-known 
Igologist, who replied as follows : 
I have never made much study of fossil algae, and would hardly feel qualified to 
rouounce on one, but my impression in this case is rather against the specimen in 
uestion belonging to the alg;e. In some respects the appearance reminds one of a 
tilota, but the branching is more regularly pinnate than in any species of Ptilota 
r ith which I am acquainted. 
From this it appears unlikely that the specimens are alga?, notwith- 
tanding the fact that they much resemble plants of that character, 
jesquereux was well aware of the doubtful nature of these plants, and 
kened them to certain partly submerged plants in which the sub- 
lerged leaves differ from the aerial ones, such as Nasturtium lacustre, 
fcc. He also suggested the possibility of their being aquatic ferns, 
'hat they really represent Selaginella seems equally doubtful, but as 
lis form maybe readily recognized, its name matters little in geology; 
ence the name given by Lesquereux is retained. 
Habitat. — Point of Hocks, Wyoming. 
Selaginella falcata Lx., emend. 
ilaginella falcata Lx., Bull. U. S. Geol. and Geog. Surv. Terr., Vol. I, p. 365 (1875); 
Ann. Rept. U. S. Geol. and Geog. Surv. Terr., 1874, p. 297 (1876); Tert. Fl., p. 
46, PI. LXI, figs. 12-15 [non PI. LXIV, figs. 13, 13a] (1878). 
Frond small, dichotomous ( ?) ; pinme, or branches, narrow, linear, 1 
> 4 cm. long, G to 7 mm. broad; leaves two ranked, close, sessile, gen- 
'ally covering each other at the borders, falcate upward, entire, 
.nceolate-pointed, suddenly narrowed to the point of attachment, 
embranaceous in texture, without middle nerve. 
This description, which is somewhat emended from that given by 
esqnereux, applies to the typical form with distichous leaves, and is 
'.presented by numerous but rather obscure specimens. As Lesque- 
>ux has pointed out (Tert. Fl., p. 47), this plant does not entirely ac- 
>rd with living Selagiuella, and hence it may not be correctly referred 
i this genus; but as it agrees in general habit and appearance with 
jlaginella better than with any other form of vegetation with which 
