4 T. G. HALLE, MESOZOIC DEPOSITS AND FLORAS OF PATAGONIA AND TIERRA DEL FUEGO. 
Flora of North America. According to later statements it would seem to be even 
younger (HAUTHAL 1907). Various explorations, dating from the time of DARWIN, 
however, have proved that strata of Lower Cretaceous and possibly Jurassic age 
have also contributed to the geological structure of Patagonia and Tierra del Fuego 
(DARWIN 1846). These Lower Cretaceous and Jurassic strata do not play any im- 
portant part, but they are known from several different districts both in the north 
and in the south. DARWIN discovered (1. c.), in a series of slates on the Brunswick 
Peninsula north of the Straits of Magellan, a marine fauna which was later described 
by ForBES (1846). The age of this fossiliferous deposit has generally been considered 
as Neocomian or Aptian. Further north there are the Lower Cretaceous faunas col- 
lected by HATCHER (1897, 1900) in the region of Lago Pueyreddon in a thick series 
of beds which he comprises under the name of the »Pueyreddon Series». HATCHER'S 
marine Cretaceous invertebrates have been described by STANTON (1901) who consid- 
ers the most important fauna to be not younger than Gault. In the same district, 
HAUTHAL has' discovered rich faunas of Lower Cretaceous ammonites of which the 
most important ones are stated by FAVRE (1908, p. 641) to indicate the Barremian 
and the Hauterivian. The exact age and the parallelisation of these different fossi- 
liferous beds are not yet exactly settled. RortH has found at Lago Fontana in 
northern Patagonia a marine deposit the age of which cannot be definitely set down 
as either Upper Jurassic or Lower Cretaceous (RotH 1908, p. 93). On the whole, it 
must be said that Jurassic deposits are very rare, and mostly somewhat doubtful, in 
the whole of Patagonia south of Piedra Pintada. RortH has found S.E. of Tecka in 
the Patagonian table-land outside the Cordillera a dolomite-like rock which contains 
some few marine invertebrates. The age of these fossils is regarded by ROTH as 
probably Jurassic and has been compared by ScHILLER with the Liassic (RorH,l. c.). 
This appears to be the most reliable account of the occurrence of Jurassic strata in 
the region south of Piedra Pintada. HaArTCcCHER (1. c.) has hesitatingly referred to the 
same formation his »Mayer River beds» from the region between Lago Belgrano and 
Lago San Martin. Since neither the upper nor the lower limit has been definitely 
determined and it has yielded no fossils which could be identified, the age of this 
series is very questionable. A Jurassic age was assumed mainly because of the great 
thickness of the overlaying Cretaceous sediments. 
The existing records of Lower Cretaceous and Jurassic deposits in different parts 
of Patagonia rendered the occurrence of fossil floras of this age very probable. Itis 
true that the deposits so far known were all of a marine nature; but in some of 
them a few poor and indeterminable plant-remains had already been noted. It was 
therefore only what was to be expected when our expedition discovered, in crossing 
the pass north of Lago San Martin, a fairly well preserved though not very rich 
flora of unmistakably Jurassic or Lower Cretaceous character. This flora is of in- 
terest in the first place because it is far remote from other floras of the same age — 
a closer inspection proved, indeed, that it is not closely comparable with any fossil 
flora in South America. It was also found to include some elements of botanical 
interest. The scope of the present paper is chiefly to describe this flora and to 
