222 
MIOCENE PERIOD. 
[Ch. XVI. 
The lacustrine strata are composed of gravel, grit, and mica- 
ceous sandstone, of such materials as were derivable from the 
surrounding primary rocks ; and so great is the thickness of 
this mass, that some valleys intersect it to the depth of seven 
Or eight hundred feet without penetrating to the subjacent for- 
mations. In one part of the series, carbonaceous shales occur, 
and several seams of coal from two to six feet in thickness, but 
no impressions of plants of which the species could be deter- 
mined, and no shells have been discovered. Many entire jaws 
and other bones of an extinct mammifer, called by Cuvier An- 
thracotherium, have been found in the coal-beds, the bone 
being itself changed into a kind of coal ; but as this species 
does not occur elsewhere in association with organic remains 
of known date, it affords us no aid in our attempt to assign a 
place to the lignites of Cadibona *. 
MIOCENE VOLCANIC ROCKS. 
Hungary.— M. Beudant, in his elaborate work on Hungary, 
describes five distinct groups of volcanic rocks, which, although 
rarely of great extent, form striking features in the physical 
geography of that country, rising as they do abruptly from 
extensive plains composed of tertiary strata. They may have 
constituted islands in the ancient SGcij clS Santorin and Milo 
now do in the Grecian archipelago; and M. Beudant has re- 
marked that the mineral products of the last- mentioned islands 
resemble remarkably those of the Hungarian extinct volcanos, 
where many of the same minerals, as opal, calcedony, resinous 
silex (silex resinite), pearlite, obsidian, and pitchstone abound. 
The Hungarian lavas are chiefly felspathic, consisting of 
different varieties of trachyte ; many are cellular and used as 
millstones ; some so porous and even scoriform as to resemble 
those which have issued in the open air. Pumice occurs 
in great quantity, and there are conglomerates, or rather 
* The author visited Cadibona in August, 1828, in company with Mr.Murchison. 
