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sheath or guard, and the alveolus. Now the alveolus is 
composed of foreign matter that has insinuated itself 
intoJ;he?chambers of the conical cavity, and becoming 
stony is easily separated from that cavity, tearing the 
fragile septa away with it, (when this consists of sparry 
matter it may be observed, that it is of a different charac- 
ter from the sheath, which confirms the opinion of the 
latter not being mineralized,) but leaving the edges of 
the septa attached to the inner almost pearly coat of the 
shell. Lamarck states the siphuncle to be central, which 
it never is in Belemnites : he has probably intended to 
include fossil Orthoceratites in the same genus. 
The strata that contain Belemnites are all above the 
New Red Sandstone ; they are, the Lyas, the inferior or 
iron-shot Oolite, the Stonesfield Slate, the Oxford Clay 
and sandy Limestone above it ; the Gault and mixtures 
of it with the Green-sand, and the lower and upper Chalk. 
It is to be remarked, that above the red marl there has 
not been seen a single straight-chambered shell with a 
central siphuncle ; nor below the red marie a single one 
the apex of which is known to extend far beyond the 
apex of the chambered cavity. In the older formations 
the substance of the chambered shells is entirely changed 
into calcareous spar, the distinction between the tissues 
of their several coats being destroyed. 
The elaborate Memoire sur les Belemnites , 4to, 1827, 
by M. deBlainville, will furnish every particular relating 
to their history, &c. which may be desired; with descrip- 
tions and figures of about fifty species ; and to that work 
we beg to refer our readers. We differ in some points 
from the opinions of the author of this excellent work ; 
