16 T. G. HALLE, MESOZOIC DEPOSITS AND FLORAS OF PATAGONIA AND TIERRA DEL FUEGO. 
the whole, a stronger dip than the contact-plane, so that the basalt comes to rest 
on younger and younger beds towards the east. 
The facts available for a determination of the age of the different members of 
this series are as yet very meagre. As has already been remarked, fossils are few 
and far between. With the exception of a small fragment of a leaf, they consist 
exclusively of invertebrates. These have been handed over to specialists for examina- 
tion, but, so far, only the Cephalopoda have been described, by Professor E. STOLLEY 
(1912) in Brunswick. Of the forms identified by him only Stilesites desmoceratoides 
STOLL. and Neolubolites ef. semicanaliculatus BLATNV. sp. are from this section. These 
both belong to the division 5: the former was found in a caleareous nodule in the 
upper part of the slates, the latter was collected among loose débris of shales occur- 
ring in such a manner that its derivation from the same division of the series cannot 
be doubted. Prof. STOLLEY has remarked that the alveole of the completest speci- 
men is filled with a solid, light sandstone, which fact would seem to be in discord 
with the supposed derivation from the division 5. I have remarked in a letter, as 
quoted by Prof. STOLLEY, that the specimen may have come from the upper portion 
of the division, in which arenaceous intercalations occur, or that the sandstone may 
be only recently cemented sand. The latter possibility is disearded by Prof. STOLLEY, 
but having seen how the sand, carried down the slopes at this locality by the always 
trickling water, is quickly cemented to a hard sandstone-like rock by the abundant 
quantity of lime held in solution. I cannot but think that this is a possible explana- 
tion especially as the rock filling up the alveole is rapidly dissolved by acids. Be 
this as it may, it is certain that the specimen in question is not derived from the 
continuous sandstoneseries here comprehended as division 6. That it could come 
from a lower horizon than 3 is contradiected not only by the conditions under which 
it was found but also by its geological age. 
Silesites desmoceratoides indicates, according to Prof. STorLEY Upper Neocomian 
or Aptian, Neohibolites ef. semicanaliculatus an Aptian age. Whether there is any 
difference between the horizons of these two species could not be ascertained owing 
to the conditions under which they were collected. They probably cannot be derived 
from very different horizons, which is also in agreement with the palaeontological 
record. According to Prof. STOLLEY, at least the upper portion of division 5 should 
therefore belong to the Aptian. It is to be hoped that the examination of the re- 
maining invertebrates will yield some further information on the age of the different 
divisions. According to a letter from Prof. STOLLEY and a passage in his paper (l. c., 
p- 6), the division 5 should embrace also Upper Jurassic beds, but details are as yet 
wanting. 
The dip of the strata in the section at Bahia dela Lancha is somewhat varied 
and irregular, but on the whole it is towards east or south-east. Tf the border of the 
meseta is followed towards the south-east younger and younger strata should conse- 
quently be met with on the same level. For some distance, there are no good ex- 
posures; but a little more than 10 km. S.E. of the south end of Bahia de la Lancha 
a small stream has cut a deep gorge through the slope of the meseta (at b on the 
