224 FOSSIL SHELLS. 



later period, are found distinct in separate families, these 

 changes would seem to indicate in the class of Fishes, a 

 process of Division and of Subtraction from more perfect, 

 rather than of Addition to less perfect forms. 



Among living Fishes, many parts in the organization of 

 the Cartilaginous tribes, (e. g. the brain, the pancreas, and 

 organs subservient to generation,) are of a higher order 

 than the corresponding parts in the Bony tribes ; yet we 

 find the cartilaginous family of Squaloids co-existing with 

 bony fishes in the Transition strata, and extending with 

 them through all geological formations, unto the present 

 time. 



In no kingdom of nature, therefore, does it seem less pos- 

 sible to explain the successive changes of organization, dis- 

 closed by geology, without the direct interposition of re- 

 peated acts of Creation.. 



CHAPTER XV. 



Proofs of Design in the Fossil Remains of Mollusks.* 

 SECTION I. 



FOSSIL UNIVALVE AND BIVALVE SHELLS. 



We are much limited in our means of obtaining informa- 

 tion as to the anatomical structure of those numerous tribes 

 of extinct animals which are comprehended under Cuvier's 

 great division of Mollusks. Their soft and perishable 

 bodies have almost wholly disappeared, and their external. 



* See note, p. 56. 



