60 
AUG. F. FOERSTE 
Whirlpool sandstone, directly beneath the layers containing the 
Leveilleites, have been described already, on preceding pages. 
Leveilleites Gen. nov. 
Specimens consisting of linear-oblong frond-like expansions 
attached to a more or less twisted stipe. Each lateral margin 
of these frond-like expansions is formed by a single series of lobes, 
the lobes being small, and those belonging to the same expansion 
being approximately of the same form and size. 
The frond-like expansions are flat and thin. Their median 
line, when the specimens are well preserved, is occupied by a 
narrowly linear black film within which no structure has been 
observed. In some specimens corresponding films occupy the 
median part of the lateral lobes. The significance of these 
linear black films is unknown. Although they occupy the 
position of a rachis, they apparently do not locate a line of 
thickening of the frond. 
The lateral parts of the frond-like expansions, as far as any 
structure has been observed, consist of fibers, more or less irregu- 
larly arranged. In most specimens these fibers anastomose 
more or less irregularly, but in a few many of the meshes are 
approximately of the same size, usually not exceeding 0.25 mm. 
in diameter. Where the narrowly linear black film along the 
median line of the frond-like expansions is absent, the fibrous 
structure characterizing the lateral parts of these expansions is 
seen. This adds to the difficulty of finding a reasonable inter- 
pretation of the significance of the linear median black films. 
In some specimens, the fibers belonging to the lateral parts tend 
to radiate more or less on approaching the margins of the lobes. 
The entire surface of the frond appears to be covered by a 
coat of very fine hair-like fibers. These fibers are seen most 
readily along the margins of the lobes, beyond which they pro- 
ject outward a distance varying from less than I mm. to fully 
1.5 mm. The finer fibers number here from 5 to 7 or 8 in a width 
of 0.5 mm. 
In some specimens, black dots are seen in addition to the 
anastomosing black fibers within the body of the frond-like 
