40 
T. G. HALLE, 
(Schwed. Südpolar-Exp. 
following diagnosis; Rami ter'etes vel subulati. Folia disticlia, alterna oppositave^ 
rhomboidea, ovalia vel lanceolata vel linearia, flabellatim vel pinnatim venosa. 
The main distinction from Pachypteris is the occurrence, in Thinnfeldia^ of a flabel- 
late or pinnate venation in the leaves, or pinnules, whereas Pachypteris was sup- 
posed, in accordance with Brongniart’s illustrations, to have only one strong simple 
vein in each pinnule. F. Braun had mentioned, in 1847 (P- Ss); ^ve new species of 
Pachypteris^ but without giving any description. Later on (1854, p. 3) he states 
that these species belong to other genera, some of them undoubtedly to llimnfeldia 
Ett. He considers the species just mentioned and EttinGSHAUSEN’s genus generally 
as distinct from his own new genus Kirchneria. This latter had been instituted al- 
ready in 1840 (p. 97), but no description was given until 1854 (p. 6; pis. i — 3), i. e. 
after EttingshauSEN’s genus was already well established. Kirchneria and Thinn- 
feldia have since been regarded as identical and the former name has been rejected. 
Several authors, relying on PHILLIPS’ figures, have conceived the errors which can 
be traced back to Brongniart’s misleading drawings. Andræ has shown clearly 
(1855) that, if Pachypteris has really several veins in each pinnule, as in Phillips’ 
figures, there is no difference between that genus and Thinnfeldia sufficient to serve 
as generic distinction. He takes the consequences of this in full, and refers ETTINGS- 
HAUSEN’S type-species to Pachypteris^ this being the older name. Andræ’s opinion, 
however, was ignored by most later authors; and since that time Thinnfeldia has 
become such a well-known genus that it has been considered as impracticable to 
change the name for the less known Pachypteris^ even though this be the logically 
right course. 
NathorsT, after having described the true nature of the venation of Pachypteris 
(1880, p. 60; see above, p. 39) states that this genus and Thinnfeldia are evidently 
identical and that the latter name, as the younger, should disappear. He recognizes 
the difficulty presented by the long established use of the name Thinnfeldia^ but 
in the list at the end of the paper (p. 84) the names Pachypteris {Thinnfeldia) cfr. 
decnrrens SCHENK and rhomboidalis Ett. are found. 
The study of both the literature and the available specimens of Pachypteris 
lanceolata has convinced me that the opinions of Andræ and Nathorst are cor- 
rect, and that there is no difference in the venation of sufficient importance to serve 
as generic distinction; indeed the venation of one of the specimens examined of 
Pachypteris lanceolata illustrates fairly well the characters on which the genus 
Thinnfeldia was founded. The natural course, therefore, would be to substitute 
Pachypteris for Thinnfeldia: the established use of the latter name could hardly be 
regarded as a valid objection against the clear rules of the principle of priority. 
There are, however, other reasons for maintaining the genus Thinnfeldia^ at least 
for the present. Thinnfeldia Ett. is, on the whole, a fairly natural genus with a 
