178 GEOLOGICAL HISTORY. 



deposits happened, so as to cover its bed very widely, first with 

 peculiar calcareous deposits (magnesian limestone), in which 

 occur for the last time a few of the old forms of life (Productae, 

 Crinoidea, &c.). 



The magnesian limestone of Yorkshire has yielded only the 

 following marine families of animal life ; the remarkable fishes 

 called Palaeoniscus, which abound in Durham and Northumber- 

 land, not being yet discovered in these strata in Yorkshire : 



Polyparia. Dimyaria. 



Bracbiopoda. Cephalopoda. 



Monomyaria. 



PAL^EOSAURIAN PERIOD. The magnesian limestone is fol- 

 lowed by arenaceous and argillaceous deposits, richly coloured 

 by peroxide of iron (New Red formations). These are almost 

 devoid of all trace of life; and if we were to judge by their 

 aspect in the North of England, we might regard them as be- 

 longing to a period really deficient of organic forms, a sort of 

 interregnum of nature separating the old Palaeozoic from the 

 new Mesozoic life. But this is not the true explanation. Else- 

 where in the South of England, and more conspicuously in 

 Europe, the new red formation contains both plants and ani- 

 mals, and they belong to the Mesozoic type. Among them are 

 the Saurians of Bristol called Palseosaurus. 



TELEOSAURIAN PERIOD. There is no proof that land had 

 been raised to represent any other part of the area of Yorkshire 

 than that already indicated in the western part of the county, 

 during the long period which elapsed while the Lias, with its 

 numerous Saurians, Ammonites, and Belemnites, was deposited 

 far to the east of the Penine hills. 



This thick series of deposits has generally an argillaceous 

 character such as might be produced in parts of an ocean 

 removed from violent currents, and receiving in abundance only 

 the finer portions of matter which could be transported far 

 before subsiding to the bottom. One exception to this occurs 

 in the midst of the deposit. The marlstone and ironstone series 



