THE GEOLOGICAL MIDDLE AGE. 
140 
Russia. The latter is, however, still under doubt 
and discussion among geologists, and more recent 
investigations tend to show that this Russian re- 
gion, supposed at first to be exclusively Permian, 
is in part at least, Triassic. 
With the coming in of the Triassic epoch be- 
gan the great deposits of Red Sandstone, Mu- 
schel-Kalk, and Keuper, in Central Europe. They 
united the Belgian island to the region of the 
Vosges and the Black Forest, while they also 
filled to a great extent the channel between Bel- 
gium and the Bohemian island. Thus the land 
slowly gained upon the Triassic ocean, shutting 
it within ever-narrowing limits, and preparing 
the large inland seas so characteristic of the later 
Secondary times. 
The character of the organic world still re- 
tained a general resemblance to that of the Car- 
boniferous epoch. Among Radiates, the Corals 
were more nearly allied to those of the earlier 
ages than to those of modern times, and Crinoids 
abounded still, though some of the higher Echi- 
noderm types were already introduced. Among 
Mollusks, the lower Bivalves, that is, the Brachio- 
pods and Bryozoa, still prevailed, while Ammon- 
ites continued to be very numerous, differing 
from the earlier ones chiefly in the over-increas- 
ing complications of their inner partitions, which 
become so deeply involuted and cut upon their 
