04 REVIEWS 
decrease in size of the canines, and a development of an arched form of 
the lower jaws. He complains that many paleontologists have not 
appreciated the law of increase in size as a fundamental one in evolu- 
tion, but, if the mammalologists have not appreciated it, surely other 
paleontologists have. 
As regards the relationships between the South American and the 
Old World and North American mammalian faunas he says: “‘ While 
the other orders are already represented in the South American Notosty- 
lops fauna, we have to deal, especially in the rodents and primates, with 
new faunal elements which must have gone thither either in the Oli- 
gocene or at the beginning of the Miocene. And they could have gone 
only from Europe or northern Africa, since, as we have seen, these 
rodents are closely related to the European forms, and the primates 
have at least a closer relationship with those of the Fayum than with 
those of the North American Eocene. There must, therefore, have 
been a connection: between South America and the Old World in the 
Oligocene or at the beginning of the Miocene.”’ ‘This theory has already 
been urged by Ameghino. ‘‘This connection could not have been a 
broad land bridge, otherwise there would have been an exchange of the 
larger mammals, which did not occur till the Pliocene.”? He suggests 
that this migration of the smaller animals may have occurred from island 
to island of an archipelago, the creatures possibly carried by the 
larger birds of prey. And he thinks also that about the same time there 
was a like exchange of the smaller mammals between North America 
and Africa. 
S. W. W. 
The Cid Mining District of Davidson County, North Carolina. By 
JosrpH E. Pocur. Raleigh: Bull. No. 22 North Carolina 
Geol. Survey, 1910. Pp. 144; Plates 22. 
This district is located in the central portion of the Piedmont Plateau 
and includes areas of slate, tuffs, volcanic breccia, rhyolite, dacite, and 
andesite, cut by gabbro and diabase dikes. All but the dike rocks range 
from a massive to a schistose condition with sericite and greenstone 
schists as the final product of dynamic metamorphism. The slates are 
interbedded with rhyolitic and dacitic tuffs. The coarser acid volcanic 
breccia grades into rhyolite flows and is thought to be a flow breccia. 
The gabbro dikes are approximately parallel to the schistosity and are 
cut by diabase dikes, said to be Triassic. The evidence as to the Triassic 
