PROFESSOR OWEN ON THE BELEMNITE. 
l / 
In neither of the above described specimens of Belemnite having the soft parts 
and phragmocone in natural connections, is there any evidence of the muscular part 
of the mantle having been continued over the capsule of the phragmocone; it is 
traceable for a short way below the peristome in Mr. Cunnington’s specimen*; but 
it is best developed where it surrounded the compressible part of the body of the Be- 
lemnite anterior to the shell. There seems no reason, however, to doubt that the skin, 
which, in existing naked Cephalopods is thin and lubricous, and more easily detached 
from the subjacent muscular layer than in the lower Mollusks, was extended over 
that part of the phragmocone extending beyond the alveolus, as there has been 
already shown evidence of its continuation over the alveolar and solid part of the 
spathose guard : its gelatinous base was less favourable for preservation than the 
fibrinous nature of the muscular tunic, and its destruction is, therefore, not surprising. 
The dark stain upon the clayey matrix, which usually extends a little beyond the 
preserved muscular structure, may in part be due to the pigmental cells of the skin ; 
and these seem evidently to have produced the thin crust of a dark greenish colour 
which hides part of the fibrous layer of the mantle in the third specimen left for de- 
scription. 
This'f-, which is from the collection of Mr. Pratt, is chiefly remarkable and valuable 
for the perfect conservation of the complex muscular structures of the head and its 
uncinated arms. Eight of these, forming the normal series of cephalic arms, may 
be defined, radiating from a contracted base. In this base may be observed two 
decussating groups of curved fibres (A), the posterior one with its concavity turned 
towards the mantle, the anterior one with its concavity directed forwards, and its 
horns continued into the bases of the arms. A similar decussated arrangement of 
fibres exists in the Onychoteuthis, and is described and figured by Cuvier in the cor- 
responding part of the head of the Octopus. Almost the entire extent of five of the 
cephalic arms is preserved, as shown in the figure; they are rather longer in compa- 
rison with the mantle than in the modern Onychoteuthis, but not as compared with 
the entire body of the Belemnite when this is lengthened out by the terminal spathose 
guard: the longitudinal arrangement of the fasciculi of muscular fibres of the arms 
is very distinct. 
I placed a portion of the muscular tissue under the microscope, and succeeded by 
the aid of a drop of diluted acetic acid in softening and unravelling the constituent 
fibres^; they presented the same size as the fibres from the corresponding part of 
one of the arms of an Onychoteuthis, but the faint transverse striee visible in the 
recent fibre § had disappeared in the fossil, and only an obscure granular structure 
could be discerned. 
Each of the arms seems to have been provided with from fifteen to twenty pairs of 
hooks || , which were doubtless developed from the horny hoops which encircled the 
caruncles of the acetabula, as in the modern Onychoteuthis. 
* PI. VI. fig. I, d. t PI. V. { Pl. VII. fig. 4. 
|| PI. VI. fig. 2, is a magnified view of the most perfect of these hooks. 
§ lb. fig. 3. 
