that the Belemno-sepicè,f from which they were
derived, attained great size.
The fact of these animals having been provided
with so large a reservoir of ink, affords an
è priori probability that they had no external
shell; the ink-bag, as far as we yet know, being
a provision confined to naked Cephalopods,
f In 1829, I communicated to the Geological Society of London
a notice respecting the probable connection of Belemnites
with certain fossil ink-bags, surrounded by brilliant nacre, found
in the Lias at Lyme Regis. (See Phil. Mag. N. S. 1829, p. 388.)
At the same time I caused to be prepared the drawings of fossils,
engraved in PI. 44", which induced me to consider these ink-
bags as derived from Cephalopods connected with Belemnites.
I then withheld their publication, in the hope of discovering
certain demonstration, in some specimen that should present
these ink-bags in connection with the sheath or body of a Belemnite,
and this demonstration has at length been furnished by
a discovery made by Professor Agassiz (October, 1834), in the
cabinet of Miss Philpotts, at Lyme Regis, of two important
Specimens, which appear to be decisive of the question. (See
PI. 44', Figs. 7, 9.)
Each o f these specimens contains an ink-bag within the ante-
rior portion of the sheath of a perfect Belemnite; and we are
henceforth enabled with certainty to refer all species of Belemnites
to a family in the class of Cephalopods, for which I would,
in concurrence with M. Agassiz, propose the name of Belemno-
sepia. Such ink-bags are occasionally found in contact with
traces of isolated alveoli of Belemnites: they are more frequently
shrrounded only by a thin plate of brilliant nacre.
The specimen (PI. 44", Fig. 1), was procured by me from
Miss Mary Anning in 1829, who considered it as appertaining to
a Belemnite. Near its lower end we see the lines of growth of
the horny anterior sheath, but no traces of the posterior calcareous
sheath; within this horny sheath is placed the ink-bag.
The conical form of this anterior chamber seems to have been
INK BAG. 375
which have not that protection from an external
shell, which is afforded by the shell of the N.
Pompilius to its inhabitant, that has no ink-bag.
No ink, or ink-bags have been ever seen within
the shell of any fossil Nautilus or Ammonite:
had such a substance existed in the body of
the animals that occupied their outer chamber,
altered by pressure. It is composed of a thin laminated substance
(see PI. 44", Fig. 1, d.), which in some parts is brilliantly
nacreous, whilst in other parts it presents simply the appearance
of horn. The outer surface o f this cup is marked transversely
with gentle undulations, which probably indicate stages
of growth. Miss Baker has a Belemnite from the inferior Oolite
near Northampton, in which one half of the fibrous cup being
removed, the structure of the conical shell of the alveolus is seen
impressed on a cast of iron-stone, and exhibits undulating lines
of growth, like those on the exterior of the.shell of N. Pompilius.
M. Blainville, although he had not seen a specimen of Belemnite
in which the anterior horny conical chamber is preserved, has
argued from the analogy of other cognate chambered shells that
such an appendage was appertinent to this shell. The soundness
of his reasoning is confirmed by the discovery of the specimen
before us, containing this part in the form and place which
he had predicted. “ Par analogie elle était donc évidemment
dorsale et terminale, et lorsqu’elle était complète, c’est-à-dire
pourvue d’une cavité, l’extremité postérieure des viscères de
l’animal (très-probablement l’organe sécréteur de la génération
et partie du foie) y était renfermée.”—Blainville Mém. sur les
Bèlemnites. 1827. Page 28.
Count Munster (Mem. Geol. par A. Boue, 1832, V. 1, PL 4,
Figs. 1, 2, 3 ,1 5 ) has published figures of very perfect Belemnites
from Solenhofen, in some of which the anterior horny sheath is
preserved, to a distance equal to the length of the solid calcareous
portion of the Belemnite (PI. 44', Figs. 10, 11, 12, 13), but in
neither of these are there any traces ol an ink-bag.