224 CATALOGUE OF THE FOSSILS OF THE PERMIAN SYSTEM 
in their composition. No other series of rocks are so complicated 
and variable in structure and appearance as these, so that it is 
almost impossible to give a description of a particular bed that 
will apply to every appearance of it. The following beds, which 
occur on the coast, are, perhaps, some of the most common and 
instructive forms presented by these rocks. 
At the end of South Shields’ sands a bed of coarse, irregularly- 
formed limestone is seen resting on, and passing into, the upper 
part of the compact bed before mentioned. It is of considerable 
thickness, and extends along the coast, nearly to Marsden Bay. 
This limestone is not sub-divided into smaller beds, but forms 
an irregular mass of a coarse concretionary structure, filled with 
shapeless cavities after exposure to the weather, and rent into 
large blocks by cracks and fissures, which cross it in almost 
every direction. In consequence of this fracturage, large masses 
are frequently disengaged from the upper part of this bed and 
are spread about at the base of the cliff. On entering Marsden 
Bay the appearance of the coast is slightly changed, and large 
piles of rock, which have for many years resisted the unceasing 
action of the tides, stand isolated among the waves. The cliff 
is here of great height, and is composed of an extensive series 
of compact and earthy laminated beds, among which irregular 
brecciated masses are situated. Some of the laminated beds are 
very hard, and of a yellowish-brown colour, emitting a foetid 
smell when forcibly struck. These are intermixed with others, 
which are of an earthy texture, and yellowish colour, and which 
are often so finely laminated that they may be easily split into 
sheets not thicker than common pasteboard. This variety is 
slightly flexible. The brecciated masses associated with these 
appear to have been formed by the breaking up of some of the 
hard laminated beds into innumerable, different sized, angular 
pieces. These pieces are confusedly mixed, and connected to- 
gether by a yellowish limestone, which serves as a cement to the 
whole mass. Leaving Marsden Bay, the cliff is composed of beds 
of an earthy appearance, intermixed with others which are slaty, 
hard, and very compact. Between Souter Point and Whitburn 
