78 
PROFESSOR OWEN ON THE BELEMNITE. 
Two small protuberances at the origin of the normal brachia are the only parts 
which represent the bases of the pair of long tentacula, superadded to the eight 
shorter arms in the existing Decapoda. 
On each side of the head, behind the bases of (he arms, there is a convex protu- 
berance formed by a well-defined semicircular band, about a line in thickness, of 
grey fibrous matter, the fibres or layers being parallel with the curve of the band. 
These parts are more distinctly shown in Mr. Cunnington’s specimen, in the descrip- 
tion of which the reasons for regarding them as belonging to organs of vision are 
given. In the present specimen they indicate, according to this view of their nature, 
that the eye-balls of the Belemnite were sessile*, and agreed in size, as in position, 
with those of the modern naked Cephalopods. 
Another specimen of similar size, in the collection of Mr. Pratt, exhibits the upper 
two-thirds of the visceral cavity formed by the mantle and the head with the bases 
of the arms, one of which is preserved to the extent of two inches, another to that of 
one inch, and on both these a few of the horny hooks remain. At the lower part of 
the head a circular amorphous granular mass is visible ; it is bounded anteriorly by 
a curved fasciculus of fibres with the concavity directed backwards : above these the 
fibres which are continued into the bases of the arms commence from a fasciculus 
curving in a direction opposite to the preceding. These decussating bands are similar 
to those in the former specimen but are more strongly marked. The fibres conti- 
nued into the arms are chiefly longitudinal. The few hooks which are preserved in 
this specimen are identical in size and shape with the more perfect series in the pre- 
ceding specimen. 
There is a minute trace on the left side, near the lower end of the specimen, of an 
obliquely striated horny plate. Most of the preserved fibrous structure of the flat- 
tened mantle is transversely arranged, as in all the other specimens ; but a faint trace 
of longitudinal or retractile fibres may be discerned near the anterior margin of the 
mantle. 
The fracture of the slabs of clay containing the last two instructive specimens has 
crossed obliquely that part of the abdomen in which is situated the striated thin 
horny plate, agreeing with that which I have ascribed to the gizzard : wanting 
therefore both the ink-bag and phragtnocone, these specimens were defective in the 
requisite evidence to associate the uncinated arms with the complex shell, muscular 
mantle, and rounded fins of the Belemnites. 
The coexistence with the true Belemnites, in the Oxford clay at Christian-Malford, 
of fossil Calamaries with a dorsal horny gladius or pen, like those from the lias at 
Lyme Regis described by Dr. Buckland'|~, made it still more desirable to obtain such 
evidence as could only be given by more entire specimens of those ancient uncinated 
Cephalopods than those above described from the collection of Mr. Pratt, which 
were the first and for some time the only specimens of the kind that I had seen. 
The subsequent fortunate discovery of the unique example^ submitted to my ex- 
* In the Nau/iltis the eyes are pedunculated. t Bridgewater Treatise, i. p. 308, J PI. III. 
