OLD Kl STONE AND DEVONIAN PERIOD. 95 



ble fossil named G . in which the septa are 



angularly folde il times, and the siphuncle 



tward as be. Q tites is the 



antecedent form of the great group of Cephalopod 

 shells allied to Ammonites y which is found in the 

 Second tta. 



On turning landward to the lacustrine deposits 



-. the first oi the great 



lakes in th< on which the old red 



ted, is that which extends 



from Coalbrookdale southward over Hereford 

 and Monmouth, and rd into Pembroke- 



shin accumulated in it is esti- 



mate D feet thick in Hereford 



d in Monmouth it includes thick 



quartz pebbles, winch may 



be 1 ed with I inch formed the Mill- 



-•it, in a lat< 1 of time. The lower 



part of this Sandstone 



ternn 



As might . overlap of 



the- n the Up| - ''nan, which is 



well 34 :: art hen. 



and in the 1 Je- 

 an of North Devon i met with in 

 lire. Hence there is-s <n(\ for 

 g that the old re hich is 

 med to have I UStrine, communicated 

 with the sea by an estuary. This may account 

 the occurrei - indifferently in 

 the marine and fresh-water beds, which are now 

 separated approximately by th< . Channel. 



All the other o. indstone deposits are re- 



garded as formed in lakes, chiefly in the lower 

 old red sandstone period. These supposed lakes 

 have been named from the geographical regions 



