1890.] Geology and Paleontology. 275 
which has been on this account generically separated under the name 
of Gryptotherium. Dr. Burmeister maintains the distinctness of 
Mastodon andium from M. huméboldt, the latter attaining a larger size, 
and having more complex teeth; moreover, the dentine in the first 
species is always red, while in the second it is white. Remains of 
Macrauchenia patachonica and M. paranensis are also described. From 
the muscular impressions still remaining on the skull it is inferred that 
the nose was produced into a short proboscis, as in the existing tapir. 
According to Dr. Roth’s recent description of the structure of the 
pampean deposits, they contain in different proportions river, wind, 
lagoon, and coast beds. The coast deposits contain sand and marine 
shells ; the lagoon beds are darker in color, and are much inferior in 
extent and thickness; while the river deposits, which contain large 
pebbles near’to the mountains, become gradually finer as they recede 
from them. The beds formed by the few streams rising in the 
pampas themselves have round, smooth’limestone concretions, as well 
as smooth fragments of bone. The zolic layers have vertical root- 
like tubes and irregular limestone concretions. The uniform character 
of the pampas loess does not, therefore, arise from its uniform origin, 
but from its long subjection to identical influences, to its transforma- 
tion under the growth and decay of vegetation, and to wind and rain. 
Water carrying down and packing loose matter often makes the loess 
of the lower parts harder than that of the higher. In Entre Rios Dr. 
Roth observed that marine beds, probably of Miocene age, were lying 
over the typical Pampean, whence he concludes that the formation of 
the pampas loess commenced in Eocene times, grew in intensity in 
the diluvial, and is continuing at the present time. 
In the Geological Magazine for January Mr. H. H Howorth puts 
forward the theory that in the mammoth age the great Siberian rivers 
flowed southward into the central lake-sea. 
