20 T. G. HALLE, MESOZOIC DEPOSITS AND FLORAS OF PATAGONIA AND TIERRA DEL FUEGO. 
Plant-remains. 
Marchantites? sp. 
Pl. 5, figs. 14—16. 
The small fragments shown in pl. 5, figs. 14—16, are very similar to specimens 
figured from different Mesozoic strata and considered to represent thalli of Hepatics. 
The present specimens are impressions of flat protracted bodies with parallel but 
somewhat sinuous sides. In the middle they show the impression of a ridge, thicker 
but less sharply set off than the midrib of a frond. From the median ridge arise 
some indistinet arching lines which taper very abruptly and rapidly disappear. One 
specimen shows a dichotomous branching. It is possible that these fragments may 
be compared with specimens described as Marchantites, but they are much too poor 
to permit of forming any definite opinion. 
Nathorstia alata n. sp. 
Pl. 1, figs. 1—9. 
According to Prof. NATHORST'S (1908) recent revision of Nathorstia HR., that 
genus is evidently the right place for a fine species of a fertile fern from Rio Fösiles. 
The best specimen, of which both counterparts were secured, is figured in pl. 1, 
fig. 1; portions of a smaller one are shown magnified in figs. 2 and 3. 
Frond pinnate, with winged rachis and opposite, distant pinnae. Pinnae entire, 
narrowly linear, up to 10—12 cm. long and 0,7 cm. broad at the base, attached to 
the side of the rachis by the whole of their bases, decurrent. Midrib of the pinna 
stout, secondary veins at almost right angles, their branches anastomosing to form 
a network of wide, often almost round meshes. BSori bordering closely on the midrib, 
placed in one contiguous row on each side. Each sorus forming a circular synangium 
containing 12—13 wedge-shaped loculi placed round a central receptacle. 
This fine frond measured at least 20 cm. in breadth. The most prominent 
feature in its vegetative characters is the disposition of the linear pinnae in pairs at 
a distance from each other equal to about the half of the breadth of the pinna. 
Between the pinnae, the stout rachis is distinctly winged, the base of each pinna 
being decurrent on the rachis to the next lower pinna. The pinnae taper very gradu- 
ally from the base and are protracted into a long and narrow apex. The aspect of 
the specimens seems to indicate that the frond was thick and leathery. In the large 
fertile specimen (fig. 1, pl. 1), the venation is very indistinet, but some smaller frag- 
ments undoubtedly belonging to the same species show the features more clearly 
(pl. I, figs. 2 and 3). It can be seen in these specimens that the stout midrib gives 
off rather distant secondary veins at nearly right angles. The secondary veins branch 
before reaching the margin into finer tertiary and quaternary veins, which anastomose 
