24 T. G. HALLE, MESOZOIC DEPOSITS AND FLORAS OF PATAGONIA AND TIERRA DEL FUEGO. 
The frond is very slender and delicate, with long, narrow rachises and small, 
thin pinnules. The specimen only represents the upper part of a bipinnate frond or 
of a pinna of a tripinnate one: it is not known, therefore, whether the frond was 
characterized by dichotomous branching. 'The pinnae are long and narrow, attached 
alternately to the rachis close to each other and directed forward at an angle of 
about 60” to the rachis. The pinnules are directed forward and are somewhat remote; 
they appear to be inserted on the upper side of the pinna-rachis, so that they overlap 
the latter. It is not possible to make out by how large a portion of the base they 
are inserted, but it does not seem probable that they are attached only in one point. 
The pinnules are ovate, with broad rounded apices and contracted and slightly 
rounded bases. The venation is distinet and characteristic. On a direct observation 
of the specimen by means of a hand-lens there is not much to be seen of the veins — 
hardly anything but the distinetly marked midribs of the pinnules. If the surface 
is moistened with cedar-wood oil, however, the venation stands out clearly differ- 
entiated. It can be seen then, that there are 3 or 4 secondary veins on each side. 
These veins arise at a fairly wide (50”—60”) angle to the midrib and bifurcate about 
half way to the margin. The two branches of each secondary vein form a remark- 
ably wide (40”—50”) angle to each other. 
Of all known species of Gleichenites, Gleichenia micromera HEER (1874, p. 55; 
pl. 10, figs. 14, 15) from the Kome beds of Greenland seems to be most closely 
related to the Patagonian specimen. HEER's species is referred by its author to the 
subgenus Hugleichenia, on account of the sori which are placed one on each pinnule, 
in its proximal half near the base. The Patagonian frond is sterile, but this need 
not prevent it from being actually referred to G. micromerus, much less so as the 
type-specimen in HEER's fig. 14 is sterile, too: the fertile pinna shown in his fig. 15 
belongs to a specimen which is from another locality and of which no other figure 
is given. There is some difference, however, in regard to the vegetative parts. The 
pinnae of the Patagonian form are directed much more forward than in HEER'S spe- 
cimen, which has quite perpendicular or even a little reflexed pinnae. The most 
important difference, according to HEER'sS description and figures, would seem to be 
in the venation. In the Greenland form, the veins are explicitly stated to be simple 
and are drawn so in the enlarged figure of the Kome specimen. In the Patagonian 
specimen, on the other hand, the bifurcation of the veins is a constant and charac- 
teristic feature, as described above, and this difference may seem to exclude the 
thought of specific identity of the two forms. An examination of the Greenland 
type-specimen (HEER, 1. c.; pl. 10, fig. 14), however, lends very little support to 
HEER'S account of the venation. The specimen, which is in the palaeobotanical mu- 
seum of Stockholm, is very poorly preserved, and it is not possible to state, even 
after a close examination, whether the secondary veins are simple or forked. Of 
HEER's drawings, only fig. 15 shows the venation, and it is possible that this spe- 
cimen, which is from another locality and of which only an enlarged portion of a 
pinna is figured, does not belong to the same species. I have not been able to find 
this specimen in the collections of the museum and can express no opinion as to 
