4 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



glomerate known as the Lower Keuper Sandstone so largely- 

 developed in our neighbourhood, particularly on the 

 Cheshire side of the Mersey, and supplying the greater 

 part of our building stone. 



These immediately underlie the beds formed by- 

 aqueous sedimentation in inland lakes, and known as the 

 Upper Keuper Marls, in which the well-known salt deposits 

 occur ; below them lie the Bunter Sandstones. The Lower 

 Keuper and the Bunter together form an alternating series 

 of hard and soft sandstones, of which the Lower Keuper 

 is the highest member. There is, however, reason to suppose 

 that some time elapsed, and some change of conditions took 

 place between the deposition of the uppermost beds of the 

 Bunter and those at the base of the Keuper ; at any rate in 

 this district the conditions altered to the extent of preserv- 

 ing certain traces of life in the Keuper and of retaining none 

 in the Bunter. At this period the old fauna of the Palaeozoic 

 rocks had disappeared, and the new forms which charac- 

 terise the Mesozoic period were coming to light. The 

 vertebrate type of skeleton had thoroughly established 

 itself, and in the course of development had reached the 

 parting of the ways. The principal forms were represen- 

 tative of the lower reptilia, but those differentiations were 

 already well marked which were to give rise to the lizards, 

 birds and mammals as we now have them ; indeed, it is 

 possible that lower mammalia had already been evolved, 

 though perhaps not present in this part of the world till 

 later. The birds are more doubtful. We have many 

 peculiarly avian characters present in some of the reptilia, 

 but of anything like a Triassic bird we have no record in 

 this country, and their course of evolution is very uncer- 

 tain. The Trias, therefore, represents a period particu- 

 larly interesting to the Biologist, and a complete know- 

 ledge of its fauna would solve many questions that now 



