48 T. G. HALLE, MESOZOIC DEPOSITS AND FLORAS OF PATAGONIA AND TIERRA DEL FUEGO. 
The position of this species in relation to the flora could not be settled by direct 
observation. As has been remarked above, it would seem that the specimen collected 
south of c is probably derived from a somewhat higher horizon than that of the 
plants, but that there can be no great difference in age. The specimen from Arroyo 
Calafate also appears to be from the lower part of division 6. TIf the few palaeo- 
zoological data available are considered, they would thus seem to indicate an Aptian 
age of the plant-bed; and, as already mentioned, the plants hitherto considered agree 
well with this result. 
There is, however, another group of plants from the same horizon which re- 
present a considerable difficulty. These are Cladophlebis australis, Ptilophyllum acuti- 
folium and Baiera cf. australis. If these three species were found isolated, they would 
doubtless have been held to prove a Jurassic age. It is important to note, however, 
that none of these forms is known from the type-areas of the European Jurassic, 
but only from the Mesozoic beds of the Gondwana continents. Cladophlebis australis 
and Baiera australis were described from Mesozoic strata in Australia considered to 
be of Middle Jurassic age, and are not known from any other district. The correla- 
tion of the plant-bearing Mesozoic deposits of Australia is a matter which has not 
yet received much attention; but there does not appear to be any reason to doubt 
that the present species should be regarded as Jurassic according to usual standards. 
Ptilophyllum acutifolium was described from the Rajmahal Group of the Upper Gond- 
wanas of India, which is considered by FEISTMANTEL to be of Liassic age. The spe- 
cies occurs also in the higher horizons, even in the Kach Group, though it is there 
to a great extent replaced by the closely allied Ptilophyllum cutchense. "The Kach 
Group is compared by FEISTMANTEL with the Lower Oolite of England, i. e. Middle 
Jurassic. As I have remarked in a previous paper (HALLE 1913), however, the usually 
accepted correlation of the Upper Gondwanas of India presents some contradictions. 
This is especially evident in regard to the highest division, the Kach-Jabalpur Group. 
The plant-bearing beds of supposed Middle Jurassic age are covered by strata with 
marine invertebrates — also to some extent occurring in association with the plants. 
These marine fossils are held to indicate the Uppermost Jurassic, and if the greater 
weight is put on the evidence of the fauna, the flora would therefore seem to be 
much younger than is generally supposed. It would appear, therefore, that the spe- 
cies persisted to the close of the Jurassic; but its occurrence in the Rio Fösiles flora, 
which, on other grounds, must be supposed to be of Lower Cretaceous age, is still 
surprising. The specific identity appears to be as certain as it can ever be in the 
case of zamitean fronds, and there is no other species with which a confusion is pos- 
sible. It must be regarded as certain that the three species now considered, viz. 
Cladophlebis australis, Baiera cf. australis and Ptilophyllum acutifolium indicate Juras- 
sic affinities, the species last mentioned being the most important one in this respect. 
The fact that these species are hitherto only known from the Gondwana continents 
may have something to do with this; and it is evident also on other grounds that 
a revision of the correlation of the Upper Gondwana floras is urgently needed. But 
in northern floras, too, there exist somewhat similar difficulties in regard to the palaeo- 
