386 THE MEDALS OF OREATION. Cuap. XI. 
superincumbent deposits, through countless centuries, and 
at length be elevated above the waters, it will constitute 
beds of shell-marble, in some mountain range, and become 
an interesting, perhaps the only memento, of the races of 
Lien. 124. SHELL-LIMESTONE; FROM THE MOUTH OF THE THAMES. 
Fig 1.—A mass of Cockle-shells and Whelks, consolidated into a 
coarse limestone. 
2,4.—One of the shells, CARDIUM EDULE, extracted from the 
block. 
3.—A slice of the rock, polished, the markings on the surface 
being derived from sections of the shells. 
mollusea and polypiaria of the present seas, when all record 
and traces of Great Britain and its inhabitants shall be 
destroyed, 
Off the Kentish coast, near the mouth of the Thames, a 
