GEOGNOSY AND GEOLOGY. 163 
but of an undulating and contorted stratification. These limestones sometimes 
alternate with bituminous and sandy limestone, tripoli, marly limestone, 
cellular limestone, &c. These masses generaliy appear in the lower portion 
of the subdivision, gypsum, karstenite, and rock salt occupying the higher. 
Magnesian limestone and dolomite are also found, and at times in immense 
beds. The former is sometimes much decomposed; the carbonate of iron 
to which it owes its blue color passes by oxydation into hydrated oxyde of 
iron, which penetrates the rock and colors it yellow, while the hydrated 
oxyde of manganese, resulting from the carbonate of manganese, is separated 
in black or dark-brown Bonacites Immense beds of chiise limestones are 
often entirely free from fossils; single layers are nevertheless characterized 
by Buccinum gregarium, Dentalium leave, Terebratula vulgaris (pl. 38, 
fig. 10), and Myophoria vulgaris (fig. 9); metallic minerals are calamine, 
galena, and brown iron-stone. 
The middle subdivision is characterized by purer limestones, of light or 
dark color, which are cften colored reddish in weathering by the 
decomposition of carbonate of iron. They form immense beds, which 
appear to be almost entirely composed of shells, the principal material of 
which has been furnished by Terebratula vulgaris and Encrinites liliiformis. 
The stem-joints of the latter, shown in jig. 7, are entirely converted into 
calcareous spar, and the axis of these pieces coincides with the axis of the 
rhombohedrons, after which the former is cleavable. The heads of such 
Encrinites ( fig. 6) are but rarely found, having generally been separated 
by destructive external influences. 
The upper subdivision contains impure marly limestones of earthy, 
somewhat plane fracture, having a great tendency to the formation of 
spheroids, and separated by clay or marl masses. Single beds consist of 
magnesian limestone, dolomite, and ferruginous brown limestone. The fossils 
here met with are particularly Ceratites (Ammonites) nodosus (fig. 11), 
Terebratula vulgaris (fig. 10), Myophoria vulgaris (fig. 9), Avicula 
socialis, Lima (Plagiostoma) striata, Nautilus bidorsatus, Pecten levigatus 
(fig. 8), Encrinites liliiformis (fig. 6), together with teeth and bones of 
Saurians and fishes. These fossils occur in a somewhat singular manner ; 
they do not lie, as in the middle division, sown indiscriminately in the 
strata, nor in single strips in the beds, as in the lower, but more on the 
faces of separation so as to lie half in the limestone, half in | the clay slate, 
~which separate the limestone strata. 
The muschelkaik is very distinctly stratified, but traversed by less regulaz 
cleavages, which sometimes widen into eaves. Like the variegated 
sandstone, it mostly forms flat troughs bounded by gently curved saddle 
formations. Higher ridges have generally rectilineal contours with rooflike 
slopes. The weathering of the muschelkalk consists of a mechanical 
division, and contributes little to the formation of a soil: the subordinate 
clay masses are of more account in this respect. Springs are rarely found. 
at high levels, more at low; they sometimes contain a proportion of salt 
when connected with deposits of rock salt. The upper division is not 
abundant, while the middle and lower are widely diffused. The muschelkalk 
ICONOGRAPHIC ENCYCLOP &DIA.—VOL. I. 38 595 
