INCERTZ SEDIS. 19 
and Ettingshausen, under the name Halyserites gracilis,’ from the 
Cretaceous of Aachen and Maestricht. This so-called alga might 
also be compared to a fragment of a filmy fern frond. 
V. 2330. Pl. I. Fig. 3. 
This specimen shows very clearly the habit of the plant, and 
especially the marked contrast between the sharply defined black 
midrib and the light brown impressions of the more delicate lateral 
portions. Ecclesbourne. Rufford Coll. 
V. 23302. Practically identical with V. 28380. Ecclesbourne. 
Rufford Coll. 
V. 2334. Several smaller pieces of the branched thalloid body : 
on the same slab of ironstone are fragments of Sphenopteris 
Fontainet, sp. nov. Ecclesbourne. Rufford Coll. 
PLANTA INCERTZ SEDIS. 
In Pl. I. Figs. 7 and 8, two specimens are represented which 
it is difficult to refer, with any degree of certainty, to definite 
genera, but which may be briefly described here as possibly 
referable to the Pteridophyta. 
Specimen A. PI. I. Fig. 7. V. 2370. 
Ecclesbourne. Rufford Coll. 
The figure shows a clearly preserved and sharply cut black 
structure projecting in a button-like form from the rock matrix. 
In the centre is a distinct depression, and from this extend 
numerous radiating ridges which curve downward at the periphery ; 
these ridges appear to be the projecting midribs of leaf-segments, 
which terminate acutely, and are fused together laterally in the 
form of a circular sheath. I am inclined to regard the specimen 
as an Equisetaceous leaf-sheath, but prefer to leave it unnamed 
in the hope of fresh discoveries affording more definite evidence 
as to its botanical position. 
1 Denkschr. k. Ak. Wiss. math.-nat. Cl. vol. xvi. 1859, p. 61, pl. i. figs. 1-2. 
