24 ITS LAND SHELLS 



cinea) is also common, while the little Chrysalis shell 

 (Pupa marginata) which lives under stones and 

 among dead leaves is often abundant and is very 

 characteristic. The following are the species that 

 have been found in the Head on the south Coast. 



Helix concinna ... f-.'iv Cyclostoma. 



nemoralis ... ... Limnea peregra. 



pulchella ... ... truncatula. 



virgata ... ... .., Planorbis glaber. 



Zua lubrica ... ... ... Pupa marginata. 



Succinea putris ... ... Limax agrestis. 



oblonga 



Bythinia tentaculata ... 



It is only when the conditions have been favourable, 

 as at Folkestone and Portland, where there are seams 

 of soft loam and fine chalk rubble, that these delicate 

 shells have been preserved. In the rough and stony 

 rubble of Devon and Cornwall they have not yet 

 been found. 



In the same way the Mammalian remains are only 

 found where there has been a matrix favourable for 

 their preservation. In the thick mass of chalky 

 rubble which underlies East Brighton they were so 

 common that Dr. Mantell designated the deposit the 

 Elephant Bed. When the Head consists of slaty 

 fragments in a sandy matrix, no bones are found, 

 owing probably to the free circulation of the surface 

 waters. That they were, however, imbedded occasion- 

 ally is proved by the fact that I found a tooth of 

 a Fossil Horse in the Head at Hope's Nose, near 

 Torquay. In the papers before quoted several instances 

 will be found of the occurrence of Mammalian remains 



