Bd. Ill: 14) 
THE MESOZOIC FLORA. 
41 
fairly characteristic venation. Though Pachypteris lanceolata has undoubtedly a 
venation of the same type, it is not a very characteristic one, and above all, it is 
not very clearly seen. The pinnules are smaller than in the typical species of Thinii- 
feldia, the veins fewer and less distinct. It would be very unfortunate, therefore, were 
Pachypteris lanceolata to be regarded as type for the genus Thinnfeldia. It seems 
better to keep Pachypteris separate from Thin>ifeldia^ and it may be possible to do 
so, though there cannot be pointed out any one distinct character sufficient alone for 
generic separation. The main difference, in addition to those already indicated, ap- 
pears to lie in the segmentation of the fronds, especially so since GoTHAN (1912) 
has lately separated from Thinnfeldia the forms with bifurcating and often bipinnate 
fronds. These forms, which are confined to the Gondwana continents, he classes in 
a new genus, Dichroidinm GoTH. \JD. odontopteroides (MORR.), D. lancifolium (MORR.), 
D. Feistmanteli GOTH., D. dubiuni (Feistm.)]. The remaining species, of Thin)ifeldia 
proper, are mostly distinguished by simply pinnate fronds. GoTHAN (/. z., p. 70) 
lays stress on this character and considers it sufficiently proved through the absence 
of pinnules on the lower parts of the rachises, which are therefore held to be the 
petioles of independent fronds. The fronds of Pachypteris lanceolata are at least 
bipinnate, though usually only detached pinnæ are found. This difference cannot 
be regarded as one of much practical value; and it is lessened by the occurrence of 
intermediate forms such as Thinnfeldia incisa Saporta (1873, p. 348; pis. 41, 42) 
and Pachypteris dimorpha Kerner (1895, p. 49; pi. 3, fig. 2; pi. 5, fig. 8). 
The principal reason for keeping, for the present, the genera Pachypteris and 
Thinnfeldia separated, however, is to be found in the relation between the type- 
species of the former and another genus, viz. Scleropteris Sap. In instituting this 
genus, Saporta (1873, p. 364) was guided by the discovery that Brongniart’s 
drawings of at least one of the type-species of Pachypteris were incorrect or repre- 
sented non-typical specimens. He considers P. ovata Brgn. as identical with Neuro- 
pteris lœvigata Phii.LIPS, and P. lanceolata BrGN. as possibly identical with Spheno- 
hteris lanceolata PHILLIPS. He therefore removes P. ovata Brgn. {Neuropteris laevi- 
gata Phillips) from the genus Pachypteris (which genus he considers should dis- 
appear altogether, if Pachypteris lanceolata Brgn. is identical with S. lanceolata 
Phillips) and places it together with sphenopteris lanceolata PHILLIPS in the new 
genus Scleropteris. It is evident from Saporta’s account of the matter that he con- 
siders the species mentioned as the types of the new genus; but he describes at the 
same time as typical members other species, of which G. Ponielii (1873, p. 370; pi. 
46, fig. i; pi. 47, figs. I, 2) is the best known. There cannot be much doubt now 
that P. lanceolata and P. ovata are identical not only with Sphenopteris lanceolata 
Philitps and Neuropteris lœvigata PHILLIPS respectively but also with each other. 
In according with Saporta’S opinion, therefore, the genus Pachypteris should be 
6 — 122943. Schtvedische Südpolar- Expedition iqoi — eçoj. 
