28o OUR COMMON BRITISH FOSSILS. 



mens go by the name of " box-stones " — a term which 

 has been given to them by the quarrymen. You 

 strike them with a sharp blow of the hammer, and 

 about one in every ten or so will break in halves, 

 revealing the cast of a fossil shell, etc., within. When 

 neatly broken, they form very interesting geological 

 specimens. Among the fossil shells thus found 

 enclosed are Pectunailns, Cardiiim^ Cassidaria, Isocar- 

 dmni, Buccinuin, etc. These " box-stones " are the 



Fig. 256. — Pecten varlus (Crag Fig. ■z.^-j.—Fissurella Grceca 



and recent). (Crag and recent). 



broken up and rolled remains of a bed of sandstone, 

 which once covered part of Suffolk, and which still 

 underlies Diest, Antwerp, Brussels, and other places 

 in Belgium, on the other side the German Ocean. 

 These "box-stones" were broken up and rounded 

 before the Pliocene period began, as is indicated by 

 the fact that they are often found coated on their 

 upper surfaces with fossil Barnacles, which clustered 

 and spread over their surfaces as they lay on the 

 floor of the shallow Red Crag sea. At Trimley, 



