10 
The specimens referred to this species are intermediate in character 
between T. lancifolia and T. Feistmanteli. The bipinnate nature of the frond 
and the narrowing at the base of the pinnae show it to be more closely com- 
parable with T. Feistmanteli. 
The Australian Thinnfeldias have been the subject of much discussion 
in the past, and there are still a number of problems to be solved in this group. 
The occurrence of the species here described is an important addition to our 
knowledge of the genus, and it suggests that wo may be dealing with an even 
more variable species than has been generally thought. 
It is expected that an examination of a representative collection of 
Mesozoic plants from Tasmania will shortly be undertaken, and when that 
is completed it may be possible to deal more satisfactorily with the Australian 
species of Thinnfeldia than at present. 
Thinnfeldia pinnata, n.sp. 
(Plate II, figs. 1-4.) 
Frond pinnate; pinnae linear, elongate, 12-5 cm. or more long, 1-8 cm. 
or more wide. Pinnules short, bluntly rounded, alternate or opposite, attached 
by vdiole base, separate or connected by narrow lamina along rachis, up to 
8 mm. long and 6 mm. broad, margins entire. Midrib w r ell defined, not reaching 
to apex, but breaking up into a number of veins. Secondary veins come off 
from midrib at an acute angle, and divide dichotomously once or twice. 
Towards the base of the frond the pinnules become more rounded and their 
midrib less prominent. 
This species of Thinnfeldia differs from other described Australian 
species, especially in the nature of the frond. Practically all those that have 
hitherto been described have either a bipinnate frond ( T . Feistmanteli ) or a 
pinnate frond in which the rachis is dichotomously forked ( T . lancifolia, T. 
odontopteroides, T. acuta), the latter feature (the dichotomous forking of the 
rachis) being very characteristic. In the present species the frond is simple 
and entire, the absence of any dichotomous forking being clearly shown by 
the lack of any modification of the basal pinnules on either side of the rachis. 
Some specimens, as, e.g., that on Plate II, fig. 1, have their basal extremity, 
very well defined, and may be considered to indicate that the fronds became 
detached by the development of a distinct absciss layer. 
