INOCERAMUS, 403 
the state of a white, friable earth, and readily decomposes, 
leaving patches of iridescent nacre on the casts; but I have 
seen examples which prove that the originals were of a 
fibrous structure, like the Inocerami of the Chalk. , 
The shells of the Inocerami, like those of the oyster, and 
other living mollusca, were exposed to the attacks of some 
parasite, and perhaps of some Annelid, as the Nereis. The 
shells are often cellular from this cause, and the cavities are 
found either hollow, or filled with chalk, or, as in the 
example Lign. 130, with flint. In the latter case, upon 
Lien. 130. FLINT, WITH FRAGMENTS OF INOCERAMUS. 
Chalk. Lewes, 
a. Marks the section of a fragment of shell, with numerous cavities, 
occasioned by the depredations of Cliona Conybearei. 
6. Portion of shell partially decomposed, and exposing siliceous, 
globular bodies, connected by filaments, which are flint casts of 
the hollows left by the Cliona. 
the decomposition of the shell, the siliceous casts remain in 
relief on the surface of the flint, asin Lign. 130, 6. Such 
Specimens are common in the broken flints of the South 
Downs, and in the shingle on the sea-shore of chalk dis- 
