mos | PROCEEDINGS OF THE NATIONAL MUSEUM. 493 
| broader and proportionally somewhat shorter than the normal ones of 
this fern. All the forms, however, are near enough to Pecopteris 
| Browniana to permit their assignment to that species with a high de- 
"gree of probability. 
& 
| Fronds bipinnate. Rachises stout and rigid. Pinne alternate, the 
basal ones much reduced in size, forming pinnules with a few broad, 
. ounded and shallow lobes. Pinnules united at base, the lower ones 
of. the pinn orbicular in shape, the others subquadrilateral, attached 
by a much broadened base, united at base, faleate, usually very obtuse 
“and remote. Basal inferior pinnule of each pinna larger than the 
‘ 
_ rest, showing three shallow rounded lobes, the lobation becoming less 
' distinct in the upper part of the frond. Nerves not seen distinctly, 
‘but apparently forming a bundle that splits up flabellately into branches. 
Fig. 2 gives the largest specimen of this fern. The basal inferior 
‘pinnules of the pinne are quite different from the rest. They are much 
larger and approximate in form the basal pinne, although much smaller 
than these. The general plan of the nervation, so far as it could be 
“made out, is similar to that of the Acrostichides of the older Mesozoic 
of Virginia. The shape, and size of the pinnules are like those of 
| Acrostichides microphyllum of that formation. In the general character 
| of the pinnules it may be compared also with Cladophlebis parva of the 
' Potomac formation. 
| {think that this is the plant reported by me to Dr. Newberry as 
| Cladophlebis parva, but the additional specimens show differences enough 
to separate them. In the absence of fructification, it would go more 
ppaturally into the genus Cladophlebis. 
In size and the form of its pinnules, it resembles some of the small 
% Bicichenias given by Heer from the Kome beds, and it is quite possible 
_ that fructification may be found that will show it to belong to that 
4 genus. Only two specimens were found, and its full character, even 
' for the sterile forms, can not be regarded as made out. 
i 
Cladophlebis heterophylla sp. nove Pl], LXxxIv, Fig. 2. 
‘' Osmunda dicksonioides Font. 
Numerous specimens of this fern occur. The imprints are in a ferru- 
-ginous, indurated shale. They coincide exactly with the Potomac 
plant. This fossil, to judge from the character of the rock which con- 
tains it, occurs at a different horizon from Aspidiwum montanense. It 
“must es been abundant in the Great Falls flora. The fructified form 
“was not seen. 
' Thyrsopteris microloba? var. alata Fort. 
i 
— Twosmall specimens of a fern closely resembling the Potomac plant, 
i Thyrsopteris microloba, var. alata, were seen in the collections. The 
; 
: 
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