162 GEOGNOSY AND GEOLOGY. 
produced by mica, chlorite, or talc ; it is also at times very thick, with double 
rectangular secondary cleavage, which, when in large beds, causes a 
tendency to a columnar structure. Quartz sandstone, whose strata are 
sometimes divided into cubes by the secondary cleavage, is limited to single 
layers. 
Fossils occur only in particular beds, and are principally constituted by 
plants, bearing most resemblance to the conifer of the torrid zone. Thus 
we have Albertia, with oval truncate leaves, inclosing the branch in horizontal 
series: A. elliptica (pl. 38, fig. 3%). Voltzia comes very near to the 
Araucariea, and constituted the greater portion of the coniferous vegetation 
of the variegated sandstone period. Their leaves are needle-shaped and 
of different forms, so that on the same branch we may see short scale-like 
leaves alternating with long needles. The cones are covered with woody 
flaps, which stand at a considerable distance apart. Voltzia heterophylla is 
generally found in the form represented in pl. 38, fig. 3°, more rarely in a 
combination of fruit-terminal and middle branches, as in fig. 4. 
LEthophyllum speciosum ( fig. 5) is another allied form. 
The upper division of the variegated sandstone, or that of the red marl, 
contains clays, marls, and sandstones, as the chief masses. Subordinated 
are quartz, granular and brittle quartz rock, this often covered with 
pseudomorphous crystals from rock salt; also limestone, oolite, gypsum, 
karstenite, rock salt, and celestine. The stratification is decided. The 
marls and clays, among which slate clay, clay marl, and marl clay belong, 
are of a reddish-brown color. Fossils occur but seldom. 
Prominent mountain forms do not appear in the group of variegated 
sandstones ; they form uniform ridges with undulating outline. The valleys 
generally run parallel to the secondary cleavages, and consequently cut 
each other at right angles. In deep valley intersections the walls are beset 
with picturesque rocks, frequently cleft, as near Kreuznach (pi. 49, fig. 9). 
In Sicily the variegated sandstone presents spacious caves (pl. 52, fig. 2). 
A sandy soil is produced by its weathering, well adapted to the growth of 
the oak and the pine. 
This group is extensively distributed. It occurs of great extent in 
Iingland, where it is known as new red sandstone; in Germany it is found 
in the Spessart, Odenwald, on the Rhone, in the Black Forest, in the Jura 
Chain, and on the west side of the Alps; also in France, Poland, United 
States, &c. 
b. Muschelkalk Group. White sandstones predominated in the last group, 
limestones of various degrees of purity do the same here; they form the 
principal masses, and are accompanied by ferruginous brown limestone, 
foetid lime, magnesian lime, clay sand marls, gypsum, karstenite, and rock 
salt. The purest limestones are generally met with in the middle of the 
group, which, receiving an addition of clay, becomes approximated to marly 
lime. Numerous individuals of few species constitute the fossils. The 
subdivisions are distinguishable, well defined by their palzontological 
character. 
The lower subdivision is indicated by marly limestones, not of a thick. 
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