CHAP. XIV. ERRATICS IN SUSSEX. 281 



mnmh' or Brittany, from land which ma}' once have existed 

 to the southwest, in what is now the English Channel. 



They were 2H-obably drifted into their present site by coast- 

 ice, and the yellow clay and gravel in which they are im- 

 bedded are a littoral formation, as shown bj" the shells. 

 Beneath the gravel containing these lai'ge erratics, is a blue 

 mud in which skeletons of Elcplias antiquus, and other 

 mammalia, have been observed. Still lower occurs a sandy 

 loam, from which Mr. E. CI. Austen* has collected thirty- 

 eight species of marine shells, all recent, but forming an 

 assemblage diflFcring as a whole from that now inhabiting 

 the English Channel. The presence among them of Lutraria 

 riKjnsa and Peeten polymorphus, not known to range 

 farther north in the actual seas than the coast of Portugal, 

 indicates a somewhat warmer temperature at the time when 

 they flourished. Subsequently, there must have been great 

 cold when the Selsea erratics were drifted into their present 

 position, and this cold doubtless coincided in time with a low 

 temperature farther north. These transported rocks of Sussex 

 are somewhat older than a sea-beach with recent marine 

 shells wliieh at Brighton is covered by chalk rubble, called 

 the " elephant-bed," which I cannot describe in this place, but 

 allude to it as one of many geological proofs of the former 

 existence of a sea-shore in this region, and of ancient cliffs 

 bounding the channel between France and England, all of 

 older date than the close of the glacial period. 



In order to form a connected view of the most simple 

 series of changes in physical geography which can possibly 

 account for the phenomena of the glacial period, and the 

 period of the establishment of the present provinces of animals 

 and plants, the following geographical states of the British 

 and adjoining areas may be enumerated. 



* Geological Quarterly Journal, vol. xiii. p. 50. 



