1835.| Geology and Paleontology. 989 
tains no Carboniferous beds. He declares that the Carboniferous 
shales and sandstones are quite distinct lithologically from the 
slates of the Boston basin, which latter, as well as the conglom- 
erate, are traversed in all directions by numerous and large dykes 
of trap or diabase, while no eruptive rocks have ever been dis- 
covered in the adjacent Carboniferous. The rocks are decidedly 
omogeneous, passing gradually into each other, and have also 
a general agreement in strike and dip. The conglomerate under- 
lies the slate, not because it is older than the slate, but because it 
was deposited in shallow water, the slate in deeper, and the latter 
deposit commenced before the first.was completed. In not a few 
instances the conglomerate can be seen to pass beneath the 
slate, 
Cretaceous—M. Ch. Arnat (Rev. Scientifique) describes the 
geological structure of the Saharan district of M? zab. is prin- 
cipally consists of an elevated plateau (hamada) of Cretaceous 
rocks, rising toward the north-east into a cliff facing the basin of 
the Oued Loua, while toward the south-east it is lost beneath the 
alluvium of the Oued Rhir. Thus this rocky plateau, which is 
entirely desolate and without running water, is bounded east and 
west by alluvial deposits. Calcareous concretions mark the pas- 
and Malmo. Those of Kristianstad are chiefly gruskalk (a lime- 
Stone composed of the fine débris of shells of mollusks and 
€chinoderms) with a mixture of quartz sand-grains and occasion- 
ally metamorphic boulders. In Ystad the prevailing rocks of the 
Cretaceous strata are incoherent calcareous sandstones, with a 
variable quantity of green grains; while in Malmo the beds are 
Pure white chalk of various degrees of hardness, with abundant 
layers and nodules of flint. These Malmo beds are an easterly 
Continuation of those of Denmark, and closely resemble those of 
