254 Hemp stead Beds. 



ter band, which is succeeded by about 40 feet of marls. 

 The limestone is a remarkable stratum, containing 

 numerous nuclei of Chara, fresh water shells, viz. Lim- 

 ncea longiscata, Paludina globuloides, Planorbis, Me- 

 lania, and of land-shells, five species of Helix, Buli- 

 mus ellipticus, Pupa perdentata, and Cydotus cine- 

 tus. Above this bed is a characteristic oyster-band 

 with Ostrea Vectensis, and this is succeeded by marls in 

 different bands highly charged with Paludina lenta, 

 Limncea longiscata, Bulimus, Melania, Unio, Cyrena 

 semistriata, C. obovata, and other fresh and brackish 

 water shells. In the Bembridge beds there has also 

 been found the Anaplotheroid mammal Dichobune cer- 

 vinum, and five species of Palceotherium, viz. P. eras- 

 sum, curium, magnum (fig. 51 ), medium, and minus ; 

 the nearest living analogues of which may be said to 

 be the tapirs of the South American rivers. 



The Hempstead Beds . form the uppermost portion 

 of the British Eocene strata. The Bembridge beds be- 

 low pass gradually into them, and the fossils throughout 

 the lower part of the Hempstead series are in great 

 measure identical with those of the Bembridge marls, 

 containing Paludina lenta in profusion, Planorbis ob- 

 tusus, Limncea, Cyrena semistriata, Unio, Melania, 

 &c., and at the very top is a marine band containing 

 Corbula pisum, and Oysters. The mammalia Hyraco- 

 therium leporinum and Hyopotamus bovinus and H. 

 Vectianus (Suidse) occur in these strata. These 

 Hempstead beds were first clearly described by Edward 

 Forbes, who considered them to be of Upper Eocene 

 age. Sir Charles Lyell, however, following Mr. Pen- 

 gelly, because of certain land plants, considered these 

 uppermost strata to be Lower Miocene. Plants afford 

 a more uncertain test of geological age than mollusca, 



