356 Rev. W. D. Conybeare on a Geological Map of [May, 



Article VII. 



Memoir illustrative of a general Geological Map of the principal 

 Mountain Chains of Europe. By the Rev. W. D. Conybeare, 

 FRS.&c. 



{Continued from p. 289.) 



Sands immediately inferior to the Chalk (Green and Iron Sand). 

 Craie Chloritee ; in some Instances, Quadersandstein 1 



This formation, where most extensively displayed in England 

 (the only country where it has yet received full attention), con- 

 sists of the following deposits, each of considerable thickness. 



1. and lowest. Beds of sand highly charged by brown oxide 

 of iron containing lignites, associated occasionally with coarse 

 limestone containing remains of turtles, crocodiles, and marine 

 shells. 



2. Blue marl. 



3. Beds of sand usually coloured by green oxide of iron, but 

 occasionally passing into the brown oxide, containing alcyonia 

 and sponges, and abundant shells often chalcedonized. 



4. Marl containing several peculiar multilocular shells (hami- 

 tes turrilites, &c), and bones of Saurian animals, passing by its 

 lowest beds into No. 3, on which it rests, and by its upper beds 

 into the inferior members of the chalk formation which cover it. 



All these varieties, however, are by no means universally 

 found even in England, and nothing beyond a general conformity 

 to the type of the series taken collectively can be reasonably 

 expected in distant countries. 



Localities. — (A.) England. 



In England, this series is very imperfectly exhibited in the 

 northern counties, where traces only of it are to be seen under 

 the chalk wolds of York and Lincolnshire, and crossing the 

 sestuary of the Wash at Hunstanton cliff in Norfolk. In Cam- 

 bridge, Bedford, and Buckinghamshire, the iron sand, No. 1, is 

 well exhibited ; but the upper members are more confused. It 

 does not indeed appear that the green sand exists as a distinct 

 deposit, but is rather blended with the marl, No. 4 (there called 

 gait). In Oxfordshire and Berkshire the tract which lies along 

 the course of these formations is low, and much concealed by 

 diluvial debris ; but insulated portions of the lowest deposit (the 

 iron sand) sometimes form summits on the ranges of the oolitic 

 hills. In Wiltshire, the green sand, No. 3, is shown in great 

 force, as also on the confines of Dorset and Devon, where it 

 forms the summit of the elevated platform of Blackdown Hills. 

 Insulated ridges of similar character extend on the west of 

 Exeter as at Haldon Hill, almost close to the transition district ; 



