158 Rhatic Beds. 



ning of the deposition of the Lias down to the present 

 day. 1 



When portions of geological history can be reduced 

 to some such form as this, it seems to possess a kind of 

 human interest in its resemblance more or less to the 

 physical geography of to-day. 2 



THE RILETIC BEDS occupy only a small space in 

 England, estimated by superficial area ; for in general 

 they run in a mere narrow strip between the New Red 

 Marl and the Lower Lias, and in fact form true beds of 

 passage from the Marl to the Liassic strata. To make 

 this statement clear it is necessary to allude to a part 

 of the geology of the Alps and of Italy. 



Professor Stoppani has described a series of strata 

 on the river Esino, in Italy, which he considers to be 

 equivalent in geological time to the Red Keuper Marls 

 north of the Alps. These strata, which he calls the 

 Infra-Lias, contain about 200 species of fossils, chiefly 

 mollusca, with a few Echinodermata and sponges, and 

 at the top lie the well-known beds called the Avicula 

 contorta zone, by Oppel, a name adopted in England for 

 these strata by Dr. Wright, when he separated them 

 from the ordinary beds of the Lias limestone and clay, 

 and correlated them with their continental equivalents. 



On the north side of the Tyrolese Alps, the Lower 



1 < Proceedings of the Royal Society,' No. 152, 1874 : Ramsay, 

 ' On the Comparative Value of certain Geological Ages ; or, Groups 

 of Formation considered as Items of Geological Time.' 



2 Though I had often lectured on some of the questions respect- 

 ing these old lakes and other points connected with the terrestrial 

 conditions of the times, it was not till 1871 that I published any- 

 thing on the subject in the papers alluded to in notes, and later, in 

 1874, in the * Proceedings of the Royal Society.' Little or nothing 

 is to be found in any Manual of Geology on the subject, except 

 in the third edition of ' The Student's Manual of Geology,' by 

 Professor Jukes, edited by Archibald Geikie, published in 1872. 



