INTRODUCTION. xiii 



forms of limestone, — in both of which places it has yielded me specimens of the above- 

 named shells. Probably the brecciated beds at the north end of Black Hall Rocks, like 

 those at Tynemouth Cliff, are partly formed of the debris of the fossiliferous limestone, 

 true beds of which are seen, at little more than a mile distance, in Castle-Eden-Dene. 

 The conditions under which the Permian Rocks of the North of England have 

 been formed, are worthy of investigation. The lowest member of the series, the 

 freestone (/), like arenaceous deposits in general, appears to have been accumulated 

 in shallow water : this view is to a certain extent proved by the presence of land 

 plants in some of its beds, as at Westoe; and by the surface of other beds being in 

 some places (Thrislington Gap) crowded with strong ripple marks. In some localities, 

 as at Tynemouth, it appears to have been accumulated in a violently agitated sea, — 

 perhaps on a coast margin, — some of its beds containing large angular fragments 

 of a purple-coloured sandstone, and having quite the character of a conglomerate. 

 The Marl-slate (e) is apparently another shallow water or littoral deposit ; as it 

 contains, in addition to A/^a, the remains of Ferns {Neuropteris Huftoniana) at Thickley, 

 and Thrislington Gap. The fishes, with which it is everywhere loaded, also attest 

 its littoral origin ; as the genera which characterise it, namely, Palceonisciis, Fi/f/opterus, 

 Coel acanthus, and Platysomus, from their abundance in certain Coal-measure deposits, those 

 of Yorkshire in particular, may be safely concluded to have lived at no great distance 

 from the shore. The presence in the Thuringian equivalent of the English Marl-slate 

 of Lingula Crechieri, Discina sjiehmcaria, Prodiictus horridus, Camarophoria SchlotheimL 

 Pleurophorus costatus, BaJcevellia antiqua, Fenestella retiformis, and probably some other 

 species, if they icere generally numerous, might be considered as strongly opposing this 

 conclusion. The next member of the system, — Compact limestone {d), concluding from 

 its mineralogical and chemical characters, and from the fragile nature of many of its 

 organic remains (Acanthocladias, Strophalosias, &c., Whitley), appears to be a pelagic 

 deposit. The same conclusion may be safely advanced with respect to the overlying 

 member, the Fossiliferous limestone (c) ; for it is impossible to conceive, that such 

 delicate organisms, as the numerous Cihobrachiate Corals, and spiney Palliobranchs 

 imbedded in it, could have existed any where except in deep water. In nearly all the 

 localities where, this limestone is seen, it has a very irregular structure, and scarcely 

 offers any appearance of stratification : it is clearly a chemical deposit ; and from the 

 circumstances noticed, I am strongly disposed to regard it as having been formed, or 

 rather precipitated, in a very rapid manner. The brecciated member il)) has evidently 

 been deposited under unusual circumstances : it nowhere contains fragments of any 

 other than Permian limestone ; but the size of these fragments, measuring, in some 

 localities, two feet in diameter (Tynemouth Cliff), and weighing, in others, several tons 

 (Ryhope)j indicates, however contiguous the parent bed froju which they were torn 

 may have been, that they were heaped together by povvcvful cataclysmal agencies. 

 The next and last member of the series, the Crystalline member {a), possesses, in its 

 often finely laminated character, that is, when observed in its normal or unaltered 



