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Fig. 15. Scaphites Equalis, from Chalk near Rouen, in the collection of Mr. J. Sowerby; the sides of the external shell are strengthened and ornamented by ribs and tubercles; and the edges of the transverse plates disposed in sinuous foliations (c.) as in Ammonites. The mouth or outer margin (b.) returns so nearly into contact with the air chambers (c.,) that the want of space at this part for the expansion of arms and head, makes it probable that the Scaphite was placed entirely within the body of its animal. (Original.)

Fig. 16. Transverse section of the chambered portion of Fig. 15, showing the arrangement of the lobes and saddles to be similar to that of Ammonites; the siphuncle also is seen on the dorsal margin at a. (Original.)

Fig. 17. Longitudinal section of the calcareous Sheath and Alveolus of a Belemnite.

a. Alveolus, or internal shell, divided by transverse Septa into air chambers. See V. I. p. 281.

b. Siphuncle, passing along the margin of the air chambers.

c. Apex of the fibro-calcareous sheath, or solid Cone of the Belemnite.

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Illustrations of the probable nature of the Animals that gave origin to Belemnites.”

*In the description of Pl. 44'. and Pl. 44". the following letters indicate the same parts in each specimen to which they are applied.

a. The Apex of the calcareous shell, or sheath.

b. Alveolar portion, or chambered shell.

c. Ink-bag.

d. ; Portions of the thin anterior horny sheath, sometimes highly

e. nacreous.

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Fig.

Fig.

Fig.

Explan ATION OF PLATE 44'. 67

1. Imaginary restoration of Belemnosepia, showing
the probable place of its Ink-bag, and of the internal
shell or Belemnite. The three component parts of
this Belemnite are represented as if longitudinally
bisected: the place assigned to this Ink-bag is nearly
the same as in the recent Loligo. (Original.)
2. Sepia officinalis, showing the position of the inter-
nal shell or sheath (Sepiostaire) within the dorsal
portion of its sac. Its apex (a,) and calcareous dor-
sal plates (e.) correspond with the apex calcareous
conical sheath of a Belemnite. -
3. Sepia officinalis, laid open along the ventral por-
tion of its Sac, to show the position of its Ink-bag.
(Original.)

Figs. 3. a. 3. b. 3. c. Rhyncholites, found in contact with

Fig.

Fig.

Belemnites in the Lias at Lyme Regis. Nat. size.
(Original.)
3. d. Beak of a small Testudo from Chalk, in the
collection of Mr. Mantell, showing a fibro-cancel-
lated bony structure, very different from the com-
pact shelly condition of the Rhyncholite, for which
it may from its size and shape be mistaken. (Ori-
ginal.)
4. Ventral surface of a Sepiostaire; the elongated
shallow cone, or cup, (e. e. e. e'.) is composed of
very thin calcareous plates, alternating with horny
membranes, which are expanded outwards to form
the thin margin of the cone. This irregular cone
or shell represents the hollow cone at the larger
extremity of the Belemnite, (Fig. 7. b. b. e. e. e".
which includes its Alveolus (b. b'.) and Ink-bag (c.)
Within this shallow sub-conical shell of the Sepio-
staire is contained its alveolus, or calcareous cham-
bered portion, (Fig. 4. b.) which represents the

Fig.

chambered alveolus in the Belemnite, (Fig. 7. b. b'.) but has no Siphon. (Blainville.)

. 4'. Longitudinal section of the apex of the shell of

Sepia officinalis. This apex is composed of granular calcareous matter (a.), alternating with conical horny laminae, which expand laterally into the horny margin (e.) (Original.)

. 5. Longitudinal view of Fig. 4. The apex (a) re

presents the apex of a Belemnite. The back of the
shell (e.) the dorsal part of a Belemnite; and the
alveolar portion (b. b'.) represents the internal cham-
bered shell of a Belemnite. (Blainville.)
6. Afterior extremity of the lamellae, or alveolar
plates, exposed by a longitudinal section in Fig. 5.
In the mature animal these lamellae are nearly 100
in number; a few of them only are here represented.
These alveolar plates form the internal chambers
of the Sepiostaire, and represent the transverse
plates of the Alveolus in Belemnites, and other
chambered shells; but as the Sepiostaire has no
siphuncle, its chambers seem not subservient, like
those of the Belemnite, to the purpose of varying
the specific gravity of the animal; the intervals be-
tween its plates are occupied by an infinite number
of thin winding partitions standing perpendicularly
between the lamellae.

Figs, 6' 6". Thin calcareous partitions winding between,

and supporting the alveolar plates of the Sepiostaire. The sinuous disposition of these partitions increases their efficacy in resisting pressure, on the same principle, as in the foliated edges of the transverse plates of Ammonites." The sinuosity of the cal

* Dr. Fleming has accurately described the structure of these partitions, as exhibiting perpendicular laminae, waved and folded in brainlike gyrations which occasionally anastomose.

Explanation of PLATE 44'. 69

careous partitions is least near the margin of the lamellae. See Fig. 6'. (Original.) Fig. 6". Columnar appearance of the sinuous partitions when viewed laterally. (Original.) Fig. 7. Unique specimen of Belemnites ovalis, from the Lias at Lyme Regis, in the collection of Miss Philpotts. A fracture at b, shows the chambered areolae of the Alveolus. At e. the thin conical anterior horny sheath originates in the edge of the calcareous sheath, and extends to e". The surface of this anterior sheath exhibits wavy transverse lines of growth; it is much decomposed, slightly nacreous, and flattened by pressure. Within this anterior conical sheath the Ink-bag is seen at c. somewhat decomposed, and partially altered to a dark gray colour. (Original.) , Fig. 8. Portion of the Ink-bag broken off from Fig. 7. c. and covered by that portion of the horny case which lay above it. The transverse lines e. on this portion, are the continuation of the lines of growth on the horny sheath of Fig. 7. e. e. e". (Original.) Fig. 9. Belemnites Pistilliformis? from the Lias at Lyme, in the collection of Miss Philpotts, having a portion of its ink-bag at c. (Original.) Figs. 10. 11. 12. Belemnites from the Jura limestone of Solenhofen, figured by Count Munster in Boué's Mémoires Géologiques, Vol. I. Pl. 4. In 10 and 12 the form of the anterior horny sheath is preserved, to a length equal to that of the calcareous shaft of the Belemnite, but in none of them is the Ink-bag visible.” (Munster.)

* Won Meyer mentions (Palaeologica, P. 322, 1st. Edit. 1832) that he has seen an Ink-bag at the upper end of a Belemnite from the Lias of Banz, and asks, “Do Belemnites possess an Ink-bag like that of the Sepia!”

Fig.

Fig.

Fig.

13. Chambered alveolar cone and horny sheath of a
large Belemnite from the limestone of Solenhofen;
the calcareous sheath or Belemnite itself has dis-
appeared. (Munster.) -
14. Belemnites brevis? from the Lias at Lyme;
Nat. size. The length of the shaft of this Belem-
nite does not exceed that of the Beloptera (Fig. 15;)
a small fragment only of its alveolus is preserved,
but the place it occupied is filled with calcareous
spar, and the hollow cone above it with lias. (Ori-
ginal.)
15. Beloptera. In this fossil we have an intermediate
link between the Belemnite and the shell or sheath
of Sepia officinalis. a. represents the apex of the
sheath, e. e. its posterior expansion, analogous to
that at Fig. 4. e. e. and at Fig. 4. e'; e' is its ante-
rior expansion, bearing on its internal surface an-
nular marks derived from the transverse septa of the
alveolus. (Blainville.)

PLATE 44". V. I. p. 282. Note.

All the figures in this Plate are of nat. size.

Fig.

Fig.

1. Anterior sheath and Ink-bag of Belemno-sepia discovered by Miss Anning in 1828 in the Lias of Lyme Regis, and noticed by Dr. Buckland (Lond. and Edin. Phil. Mag. May, 1829, P. 388,) as “derived from some unknown Cephalopod, nearly allied in its internal structure to the inhabitant of the Belemnite.” This sheath is, for the most part, nacreous; in some places (d. d) it retains the condition of horn. The corrugations on its surface indicate the lines of growth. At f: a transverse fracture shows the neck of the ink-bag. (Original.)

2. The lower part of Fig. 1. seen from another side;

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