214 
MIOCENE PERIOD. 
[Ch. XV. 
and concretionary limestone of a yellowish white colour : it is 
finely exposed in the escarpments of Wildon, and in the hills 
of Ehrenhausen, on the right bank of the Mur *. This coral- 
line limestone is not less than 400 feet thick at Wildon, and 
exceeds, therefore, some of the most considerable of our 
secondary groups in England, as, for example, the ' Coral 
Ragf.' 
Beds of sandstone, sand, and shale, and calcareous marls, are 
associated with the above-mentioned limestone. 
The third group, which occurs at a still greater distance 
from the mountains, is composed of sandstone and marl, and of 
beds of limestone, exhibiting here and there a perfectly oolitic 
structure. In this system fossil shells are numerous. 
It is by no means clear that the coralline limestones of the 
second group, are posterior in origin to all the beds of the first 
division ; they may possibly have been formed at some distance 
from land, while the head of the gulf was becoming filled up 
with enormous deposits of gravel, sand, and mud, which may, 
in that quarter, have rendered the waters too turbid for the 
fullest development of testaceous and coralline animals. 
In regard to the age of the formations above described, we 
may observe that the middle group, both in the basins of Styria 
and Vienna, belongs indisputably to the Miocene period, for 
the species of shells are the same as those of the Loire, Gironde, 
and other contemporary basins before noticed. Whether the 
lowest and uppermost systems are referrible to the same, or to 
distinct tertiary epochs, is the only question. We cannot doubt 
that the accumulation of so vast a succession of beds required 
an immense lapse of ages, and we are prepared to find some 
difference in the species characterizing the different members 
of the series ; nevertheless, all may belong to different sub- 
divisions of the Miocene period. Professor Sedgwick and Mr. 
Murchison have suggested that the inferior, or first group, 
which comprises the strata between the Alps and the coralline 
* Geol. Trans., Second Series, vol, iii. p. 3S5. -j- Ibid., p. 390. 
