Bd. III: 14) 
THE MESOZOIC FLORA. 
39 
Genus Pachypteris Brongniart. 
The institution of the genus Pachypteris Brgn. and especially the misleading 
drawings by which it was originally accompanied have been the source of much 
confusion in the classification of related forms. According to the first diagnosis of 
Pachypteris^ in Brongniart’s “Prodrome”, 1828, p. 49, the genus is distinguished, 
apart from the thick and coriaceous nature of the fronds, mainly by the absence of 
a visible venation or the occurrence of one simple vein in each pinnule. The illustra- 
tions given in the »Histoire des végétaux fossiles» represent the two species referred 
to the genus, viz. P. lanceolata and P. ovata (1829, pi. 45, figs, i, 2), as possessing 
pinnules with strong, simple midribs. As synonyms are given, in the same work 
(p. 167 — 168), and no doubt rightly, Sphenopteris lanceolata Phillips (1829, p. 153; 
pi. 10, fig. 6) and Neuropteris lævigata PHILLIPS (ibid. p. 154; pi. 10, fig. 9) re- 
spectively. In the second edition of PHILLIPS’ work (1835) both species are retained 
under the same names as in the first. The illustrations given differ widely from 
those of Brongniart in regard to the venation of the pinnules. Both species are 
figured as having no distinct midrib but a number of secondary veins which seem 
to radiate, in Neuropteris Icevigata from the base of the pinnule, in Sphenopteris 
lanceolata from the median portion of its lower half. Nathorst, who discussed, in 
1880 (p. 59), the affinities of Pachypteris^ states that in two specimens examined 
the pinnules had an almost imperceptible midrib, or none at all but, as it appeared, 
lateral veins diverging towards the edges. In a third specimen there was a midrib 
or perhaps rather a midrib-like impression reaching to the middle of the pinnule. 
Seward (1900, p. 171), after Schimper (1869, p. 492), joins Phillip.s’ two species 
under the name Pachypteris lanceolata Brgn. Pie states that the pinnules were 
probably traversed by several veins but does not mention whether a midrib occurs, 
too, or not. 
A specimen collected by the writer in Yorkshire confirms Nathorst’s and 
Seward’s statements in all respects. In some of the pinnules there is, on the im- 
pression, a distinct median groove which may well be caused by a midrib, in others 
it is imperceptible. In a few of the pinnules, also in those without a midrib, there 
are seen a number of subparallel lateral veins slightly radiating from the midrib or 
the line in which it would be expected to occur. 
It will be clear that the venation, as described by Nathorst and above, and 
as shown in at least one of PHILLIPS’ figures (pi. 10, fig. 6), is essentially that of 
the genus Thinnfeldia Ett. This genus, in fact, was instituted under the influence 
of Brongniart’s misleading illustrations. Ettingshausen (1852, p. 2) considers the 
specimens referred to his new genus as branches of coniferous plants and gives the 
