290 OUR COMMON BRITISH FOSSILS. 



Red Crag into two series — the lower, characterized by 

 oblique lamination ; and the upper by persistent hori- 

 zontal bedding. The lower part is much richer in 

 shells than the upper. The most abundant in the 

 Red Crag are the Common cockle, Cardiiim angusta- 

 tum^ Pectimcidus glycimeris, Tellina crassa^ T. obliqtca^ 

 Mytihis edulisy Pecten opercularis^ Cyprina islandica, 

 Lticina borealis, Cardita senilis ^ 

 Purpura tctragonUy P. lapillusy Tro- 

 phon (or Fustis) antiques, T. con- 

 trarius^ Nassa reticosa, N. gramdata, 

 Astarte Omallii, Cyprcea Enropceay 

 etc. In many places, as at Tatting- 

 ^stone, Bentley (in the pits near the 

 station), Foxhall, Bucklesham, and 

 elsewhere, the strata teem with 

 Pectuncttclus, Trophon contrariuSy 



fig. .z,,^'purMra tetra- Cardita seuiUsy Nassa, etc. 



.-^««tcragbeds). jj^^ numbcr of species of fossil 



mollusca belonging to the Red Crag is two hundred 

 and thirty-four, of which two hundred and sixteen are 

 still in existence. In addition to this number, we 

 must include about forty extraneous species. About 

 one hundred and fifty of the above species ?.re still 

 living in British seas, whilst of the remainder, thirty- 

 two are southern forms, and twenty-three northern — 

 a total of nine more northern species than are found in 

 the Coralline Crag, thus far indicating a refrigeration 

 of the climate. 



