388 THE MEDALS OF CREATION. Cuap. XI. 
AS = kA 
Fossiz SHELLS oF THE Bracuiopopous Mo.ivusca.— 
These are bivalve shells, of which nearly five hundred species 
are found in the British strata. They occur in incredible — 
4# 
Lien. 125. TEREBRATULA AND RHYNCHONELLA; nat. 
Chalk. Lewes. 
Fig. 1.—RHYNCHONELLA PLICATILIS. 
la.—The same species, partly open. 
2.—RHYNCHONELLA SUBPLICATA. 
2a,—Front view of the same. 
3.—TEREBRATULA SEMIGLOBOSA; side view. 
3a.—The same species, seen from above. 
4,—TEREBRATULA SUBROTUNDA. 
numbers in the ancient rocks, to which several genera are 
restricted ; while some continue through all the formations, 
