INOCERAMUS. 
129 
interesting memoir, published in the Geological 
Transactions, voh ii. 
The shells of the larger Inocerami, appear to 
have been subject to the ravages of a peculiar 
parasitical animal, which destroyed the intermediate 
substonce, leaving the outer and inner plates en- 
tire, and supported only by thin partitions. The 
specimens exhibiting these appearances are full of 
small oblong cells, connected by linear perforations; 
and these are either empty, or filled with chalk or 
flint ; in the latter case, they give rise to a curious 
class of fossils, the nature of which JVTr. Conybeare 
has very ingeniously explained. 
SILICEOUS CASTS FORMED IN CELLS PRODUCED IN THE SHELLS 
OF THE INOCERAMI BY PARASITES. 
A specimen of this kind is here represented ; 
it is part of a flint, moulded in the interior of 
an Inoceramus, having on its surflice numerous 
irregular oblong bodies, more or less compressed, 
and united to each other by slender lateral fila- 
ments. 
The investigations of Mr. Conybeare have 
clearly shown “ that these are silicious casts, 
formed in little cells, excavated in the substance 
of certain marine shells, the work of animalculm 
preying on those shells, and on the vermes inha- 
K 
