46 
T. G. HALLE, 
(Schwed. Südpolar-Exp. 
the pinnules. The latter vary much in shape, too, especially in regard to the pro- 
portion of length and breadth. They are, however, always attached to the rachis 
by a narrow base and are not decurrent. The edges of the lamina are often nearly 
straight, and in that case there are sharp corners at the point of the greatest breadth, 
about 7 s from the base. This feature, which is seen, for instance, in text-fig. lo a 
and â, gives to the pinnules a characteristic rhomboidal aspect. The venation is 
usually very distinct, and thereby this species is very different from the one de- 
scribed as Pachypteris dahnatica. The secondary veins are rather few and distant, 
but strong and persisting to the margin. Their forward direction and straight course 
accentuate the T!iin)ifeldia-\\ah\t of the venation. 
As may be seen from the figures, the different specimens of this species display 
a great variation, which is expressed especially in the relative breadth of the pin- 
nules. As two extreme instances the specimens in pi. 4, fig. 30, and in text-fig. 
10 a may be brought into comparison. There is, however, a fairly continuous 
series of transitional forms; and there is no doubt that all these specimens should 
really be referred to one species. The largest frond appears to have been the 
one in pi. 4, fig. 34: it is remarkable also for the abruptly tapering bases of the 
pinnules. 
The present species seems to come very near to Thmnfeldia indica Feist- 
MANTEL (1877 a, p. 35; pi. 39, fig. i; pi. 46, figs. I, 2) from the Indian Gondwanas 
and was at first considered identical with that species. Some specimens, which were 
discovered later, cast more doubt however on the identity of the Antarctic form 
with Thinnfeldia indica. Our specimens differ from that species in several respects, 
especially in habit. Th. indica is much larger with a very stout rachis, also it has 
more asymmetrical, somewhat falcate pinnules and the bases of the pinnules are 
more decurrent on the rachis. On the whole, though the resemblance is fairly close, 
it is certainly not sufficient to warrant specific identity. The habit of some of the 
Antarctic specimens and the shape of their pinnules agree still more with Thinn- 
feldia rhoniboidalis Ett.; but in that species the pinnules have a broad decurrent 
base, and are usually shorter and broader. In regard to the bases of the pinnules 
and their mode of attachment, there is a certain resemblance to Thinnfeldia speciosa 
Ett.; but the pinnules of that species are of a different shape, much more elongated 
and narrow. On the whole, the Antarctic species may be said to occupy an inter- 
mediate position between Th. rhoniboidalis and Th. speciosa., resembling at the same 
time Th. indica, from which it differs also through its much more slender habit. 
Finally, a specimen from Queensland, figured by JACK & Etheridge (1892; pi. 17, 
fig. 2) as “ Th. media Ten. Woods.? or Th. indica Feistm..?” but rather different 
from both these species, must be mentioned as very similar to and perhaps identical 
with the Antarctic form. 
