202 
A. B. Walkom, D.Sc. 
LYCOPODIALES. 
Isoetites elegans, sp. nov. 
(Plate I.) 
Leaves numeroxis, long (up to 12 cm. or more), straight or slightly curved, 
about 3-4 mm, wide at base, tapering to apex, with very fine parallel striations. 
Sporangia usually 1*5-2 cm. long, by 7-8 mm. Megaspores spherical, about 
0*5 mm. in diameter, smooth, with equatorial ridge, and tri-radiate marking 
on one hemisphere, 40-55 megaspores in a sporangium. 
In the specimen figured (Plate I., fig. 1) there are some 30 leaves visible ; 
in addition the bases of a number of other leaves can be observed on the vertical 
edge of the specimen, so the total number of leaves is greater than 36. The 
leaves are all simple and there is no indication of dividing as occurs in Baiera 
and allied genera. The tapering of the leaf is very gradual — from 3 4mm. 
wide at base to 1 mm. wide at a distance of 12 cm. from the base. 
The sporangia vary little in shape, but they may b(^ <livided into two 
distinct groups — one in which the individual megaspores are clearly visible, 
the other in wLich little or no structiire can be obser\'ed (see Plate I., fig. 2|. 
There is some indication in a few of the latter type that the sporangia contain 
megaspores, outlines of which can be observed. It may be, however, that 
the majority of these sporangia wdiich show no structure now were the micro- 
sporangia and that no details of the microspores are preserved in the specimens 
available. 
The megaspores (Plate I., figs 4. 5), with their equatorial ridge and the 
tri-radiate marking on the upper half, are of the type characteristic of Isoetes 
and, from the association of the sporangia with the specimen in which the 
leaves are so similar to those of species of Isoctes, it is reasonable to conclud(' 
that sporangia and leaves belonged to the one species and to refer them to 
the genus Isoetites. There is indeed evidence that the sporangia occupied the 
position usual in Isoetes, several specimens, of which one is figured (Plate I., 
fig. 3), showing a sporangium resting on the wide basal portion of a leaf. 
Some specimens, such as that figured on Plate I., lig. 2, show a number 
of sporangia (megasporangia and ? microsporangia) arranged more or less 
parallel to one another. Some of those on the figurecl specimen have some in- 
dication that they rest on portions of leaves. 
In size and shape these fossil sporangia are well within the range of those 
of recent species of Isoetes^ as also are the megaspores. The range of size of 
megaspores in recent species is from 250 to 900 p. Such species as Isoetes 
Engelmanni and I. Boryana w'ould bear comparison with our fossils in this 
respect (see Pfeiffer, 1922). 
There are few recorded fossils that can with certainty be referred to 
Isoetites, so that comparison of the Western Australian specimens witli known 
species is restricted. The leaves are very different from those of 1. serratus 
and I. horridus from Cretaceous rocks in Wyoming, U.S.A. (Brown, 1939, p. 
268) and no details of the megaspores are known in these two species. 
The fossils described as Isoetites Choffati Saporta from the Lower Cret- 
aceous of Portugal are not comparable with our specimens, since they consist 
of small tuberous bodies compared with the stem of Isoetes, and imj^ressions 
identified as the basal portions of sporophylls bearing sporangia (fide Seward, 
1910, p. 67 — a copy of Saporta’s original description does not appear to be 
available in Australia). 
