1871.] KAMSAT LOWEE LIAS. 197 



number of genera and species ; and some of the forms are poor and 

 dwarfed. It is a north-sea fauna ; and when the area was first 

 separated from the maia ocean, it was first freshened by influx of 

 rivers, while it is now agaia becoming salter by evaporation. The 

 result is the poverty and dwarfing of the forms. In the Black Sea 

 there are misshapen or monstrous forms of Mollusca, stated by 

 Forbes to be due to the freshened state of the water. Both of these 

 cases, relating to what may be called continental seas, bear upon 

 the subject in question, especially since the Ehaetic fauna of 

 England is also comparatively poor in genera and species, when com- 

 pared with the weU-developed fauna of Lombardy and other parts 

 of the south and east of Europe. 



I now come to a difficult point. It is undoubtedly true in England 

 that the Lower Lias follows the Ehgetic beds wherever they go ; and 

 though there are symptoms of erosion between them at Penarth and 

 at Curry RiveU, in Somerset*, yet the conformity is, on the whole, so 

 complete, that wherever we meet with the base of the Lower Lias 

 we look for the Ehsetie beds below, and as yet we have not been dis- 

 appointed. The question then arises, how is it that the transition 

 in these areas from the Khsetic to the Liassic forms is so sudden ? 

 It is hard to answer this question ; but it may perhaps be met by an 

 analogous case. The estuarine and the lagoon beds of the Purbeck 

 and Wealden series commenced in the Oolitic epoch, and ended in 

 the Neocomian or Lower Cretaceous epoch ; and the change be- 

 tween the life of the Oolitic and Keocomian and Cretaceous de- 

 posits is as great as, and in some respects greater than, that between 

 the Rhsetic and Liassic strata ; and though the Ehsetic beds were not 

 deposited in fresh water, yet, like parts of the Purbeck series, I 

 believe they were formed in shallow water under brackish semi- 

 estuarine conditions which endured for a long period. 



In conclusion, I may state that the same kind of reasoning, with 

 differences, applies more or less to other red-coloured and to some 

 calcareous strata of England," including the Permian, Old Red Sand- 

 stone, and even the red Cambrian formation. This I hope to treat 

 of in a subsequent memoir. If this idea is true, and if this kind of 

 work be carried out, it must have an important bearing on certain 

 departments of palaeontology in a manner already partly indi- 

 cated by Professor Huxley, and it may throw much light on the 

 distribution of the various forms of animal and vegetable life in 

 time and space. Without it, we must still in great part continue 

 to regard the various formations very much as we might a pack of 



in which the beds were being very tranquilly deposited " (" Abnormal Secondary 

 Deposits," Quart. Journ. Geol. Soc. 1867, vol. xxiii. p. 470). See this memoir for 

 a great deal of valuable information on these and other deposits. See also 

 memoir by Dr. Wright " On the Avicula-contorta beds," Quart. Journ. Geol. 

 Soc. 1860, vol. xvi., and others. 



* This kind of erosion was evidently not accompanied by marked uncon- 

 formity, the result of serious disturbance of the Ehffitic beds before the deposi- 

 tion of the ordinary Lias. Estuarine or tidal sea-currents would have been 

 suiRcjent to produce it when the Lias-sea first came across a slowly sinking 

 area. 



