FOSSIL SHELLS. 295 
In no kingdom of nature, therefore, does it 
seem less possible to explain the successive 
changes of organization, disclosed by geology, 
without the direct interposition of repeated acts 
of Creation. 
Chapter XV. 
Proofs of Design in the Fossil Remaiiis 
of 3Iollusks.^ 
SECTION I. 
FOSSIL UNIVALVE AND BIVALVE SHELLS. 
We are much limited in our means of obtaining 
information as to the anatomical structure of 
those numerous tribes of extinct animals which 
are comprehended under Cuvier's great division 
of MoUusks. Their soft and perishable bodies 
have almost wholly disappeared, and their ex- 
ternal shells, and, in a few cases, an internal 
apparatus of the nature of shell, form the only 
evidence of the former existence of the myriads 
of these creatures that occupied the ancient 
waters. 
The enduring nature of the calcareous cover- 
* See note, p. 62. 
