178 
DR. MANTELL ON BELEMNITES, ETC. 
Clay of Wiltshire are not symmetrical ; but the apex of the cone inclines to one 
side in consequence of the position of the axis of the guard, and terminates in a 
very fine point, as in the example, fig. 4. In this specimen the cells are filled with 
calcareous spar, as is frequently the case with that portion of the phragmocone 
which is implanted in the alveolus ; a fact doubtless connected with the similar 
mineral state of the osselet itself. The latter is almost invariably saturated as it 
were with crystallized carbonate of lime of a brown colour and radiated structure ; 
for notwithstanding the microscopical observations of Dr. Carpenter and Professor 
Owen, 1 think the evidence is in favour of the conclusion of the Dean of Westmin- 
ster, that this crystalline condition has resulted from sparry infiltration, subsequently 
to interment, into the cellular and radiated calcareous texture of which the osselet 
was originally composed* ; in like manner as the crustaceous coverings and spines 
of the Echinoderms in the Oolite and Chalk, are so saturated with calc-spar as to have 
acquired the hardness and peculiar oblique fracture of the crystalline mineral matter. 
The facts above described appear to me to confirm the opinion advanced by Mr. C. 
Pearce and Mr. Cunnington, that the Belemnoteuthis is generically distinct from the 
Belemnite. In addition to the discrepancies in the form and structure of the phrag- 
mocones of the respective Cephalopods, pointed out by these observers, the specimen 
represented, Plate XV. fig. 3, demonstrates that in the Belemnite there are two other 
essential characters of which no traces have been detected in the Belemnoteuthis ; 
namely, the periostricum, capsule, or external corneo-calcareous investment (c', c, c ) ; 
and the processes that extend from the basal margin of the visceral chamber (b, b'), 
the peristome of the Belemnoteuthis being entire (Plate XIV. figs. 3, 4). It is worthy 
of remark, that the surface of the capsule of the Belemnite, and that of the phrag- 
mocone of the Belemnoteuthis, are alike smooth and glossy ; as if in the one the 
osselet, &c., and in the other the chambered shell, were originally wholly enveloped 
by the mantle. But the exterior of the siphonated phragmocone of the Belemnite is 
devoid of polish, and is in such close contact with the walls of the alveolus, that it is 
very rarely the shell can be displayed entire as in the specimen, Plate XV. fig. 4. 
If it be contended that upon physiological grounds the phragmocone of the 
Belemnoteuthis must have been implanted in the alveolus of a guard or osselet, I 
would reply that none of the species of Belemnites with which these chamhered 
cones are associated in the Oxford Clay of Wiltshire, can have belonged to them, for 
the reasons already assigned ; and a guard has still to be discovered that shall meet 
the exigencies of the case. If, therefore, with our present scanty information, we 
affirm that the Belemnite and the Belemnoteuthis belong to one and the same genus, 
I respectfully submit that we are not only reasoning in advance of the data hitherto 
obtained, but contrary to known facts. 
From a tolerably extensive knowledge of the fossil Cephalopoda of the argillaceous 
strata of the Oolite and Lias, I am led to conclude that the Oxford Clay of Wiltshire 
* Bridgewater Essay, p. 372, 
