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TNOCERAMUS. 
or less gibbous, and are commonly marked with trans- 
verse concentric ridges, and striae ; their constituent 
substance is invariably composed of crystallized 
carbonate of lime, of a radiated or fibrous structure. 
The hinge is a longitudinal furrow, transversely 
crenulated, extending on one side of the beaks 
only ; its direction, as it regards the transverse 
diameter of the shell, being generally oblique. 
One species, the Inoceramus Cuvieri attains a 
large size : a fragment in my cabinet indicates a 
length of three feet, by two feet in width. An 
example of Inoceramus Lamarckii, which shows the 
hinge, is figured below, and will serve to convey a 
correct idea of the character of the genus. 
INOCERAMUS LAMARCKII. 
We cannot omit to notice here the curious fossil 
bodies that are occasionally observed on our flints, 
and which have been considered by some naturalists 
as silicified zoophytes. Their nature was first 
])ointed out by the Rev. W. Conybeare, in a very 
