kidston: the flora of the carboniferous period. 191 
stalk, or cuneate, and even almost filiform. Nervation radiating 
from the base of the pinnule and frequently dichotomising. 
The chief genus is Sphenopteris Brongt. 
Sphenopteris Brongt. The general characters of one of the 
sections of the ferns commonly included in Sphenopteris is well 
represented by Sphenopteris obtusiloba Brongt. (Plate XXV., 
fig. 1). The pinnules are oval entire, lobed, or divided into 
3-5 segments — their form varying according to their position on 
the pinna. The dichotomising veins radiate fan-like from the 
base of the pinnules (Plate XXV., fig. la). 
Another section of Sphenopteris has pinnules with more or 
less cuneate segments, of which Sphenopteris /areata Brongt. may 
be taken as a typical representative (Plate XXVII. , fig. 2). 
The segments of the pinnule are narrow, linear, with a veinlet 
running into each tooth (Plate XXVII., fig. 2a). In both of 
these sections there are some species with very small pinnules. 
Although one must be very careful in generalising, still it 
seems as if the linear or cuneate pinnuled forms were more 
characteristic of Lower Carboniferous rocks, while those with 
rounded lobed pinnules were more typical of the Upper Car- 
boniferous. Both types, however, occur together in all the 
divisions of the Carboniferous Formation. 
Many species originally included in Sphenopteris have had 
special genera provided for their reception. In some cases the 
characters are derived from the mode of division of the pinnse 
— characters dependent on the vegetative system. It appears 
to me very doubtful if any real advantage is derived from the 
creation of such genera, as they cannot be regarded as other 
than provisional, and personally I prefer retaining the ferns 
placed in these genera in Sphenopteris. As examples of the 
genera to which I refer, Palmatopteris Potonie (of which 
Sphenopteris furcata is the type), and Diplothmema Stur may 
be mentioned. 
The other class of genera which have been taken from 
Sphenopteris Brongt. hold, however, a very difierent position, as 
they are founded on characters which are derived from their 
