264 



OUR COMMON BRITISH FOSSILS. 



retain, when dug out of the stiff clay, the rainbow 

 hues of the nacre or mother-of-pearl coating. But the 

 shells are fragile, and the tints evanescent, unless 

 means are taken to preserve them. The commonest 

 of the bivalve and univalve fossils are Inoceranms 

 sulcattis, Plicatula, Dentalmm^ Rostellaria, etc. Out- 

 crops of Gault clay, containing fossils, are worked at 

 Barnwell, near Cambridge, but the chief hunting- 

 ground has long been 

 Copt Point, Folkestone, 

 which is classic on that 

 account. In Norfolk, the 

 Red Chalk of Hunstan- 

 ton — which stands forth 

 in such vivid relief from 

 the green strata below 

 and the grey chalk above 

 it — is usually regarded 

 as of the same age as the 

 Gault. It is in places 

 full of small Belemnites, 

 like those obtained from 

 the Gault, and contains 

 numerous Inocerami and 

 Ostrea. The Greensand of Cambridge rests on the 

 Gault, and is crowded with fossils which have been 

 washed out of that deposit. The Upper Greensand 

 occurs in Devon, Somerset, Sussex, Kent, Isle of 

 Wight, Dorsetshire, etc. Its chief fossils are Pecten 



Fig. 243. — Inocerainus Cuvieri 

 (Lower Chalk). 



