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ExPLANATION OF PLATE 30. 51
larger and superior Plate overlapping the edges of the next subjacent and smaller plate. These edges are rendered more irregular by decomposition. d". Magnified representation of very minute curved lines passing from the marginal band across the shaft, at d. e. Thin lamina of the white pulverulent substance of a decomposed Plate; it retains partial traces of the transverse wavy fibres. f. Minute perpendicular filaments prevailing over th transverse fibres of the shaft. Fig. 3. Fossil Loligo from Lyme Regis, showing the same structure as the preceding figures, in the several portions of the Pen that are preserved ; and having its Ink bag distended nearly in its natural shape and place beneath the Pen. (Original.) C.C. Axis of the shaft. Figs. 4. 5.6.7. S. 9. Fossil Ink bags from Lyme Regis. The membranous sacs and excretory ducts are still preserved, and closely resemble those of a recent Ink bag; see Pl. 28. fig. 5. (Original.) Fig. 10. Fossil ink bag found by Miss Anning in the Lias near Watchet, Somerset. (Original.)
Plate 30. V. I. p. 234.
A large fossil pen of Loligo; from the Lias at Lyme Regis. In the collection of Miss Philpot. (Mrs. Buckland. Original.)
AA. Barbs of the pen, proceeding from the outer edges of the marginal bands.
B.B. Marginal bands dividing the bases of the barbs from the internal part or body of the shaft.
C. Axis of the Pen, dividing the body of the shaft into two equal parts.
D. Transverse section across the Ink bag. d. First or upper plate. This plate is very thin, and smooth, and its structure is obscure, except on the right marginal band at d', where the longitudinal ridges on its surface are very distinct. e. Upper surface of second plate, marked with broad wavy lines, passing on each side from the axis outwards, across the body of the shaft, and over the marginal bands. f. Upper surfaces of a third plate, exhibiting minute curved striae, ascending symmetrically in opposite directions from each side of the axis of the shaft C, and descending towards its margin. These curved striae are intersected by minute longitudinal straight lines, running nearly parallel to the axis of the shaft. Towards the apex of the shaft at f", the broad transverse curves predominate over the fine longitudinal fibres which lie beneath them. At g, no transverse curves are visible." (Mrs. Buckland. Ori
- PLATE 31. V. I. p. 240.
Fig. 1. Animal of Nautilus Pompilius, fixed in its shell. The shell is copied from one in the collection of Mr. W. I. Broderip. (Animal from Owen. Shell original.) * n. The Hood, or ligamento-muscular disk that surrounds the head. p. The digital tentacles protruded from their sheaths. k. Funnel. a. b. c. d. e. Siphuncle. The desiccated membrane of
* Herman von Meyer (Palaeologica, 1832, P. 322) mentions the occurrence of ink bags, together with the horny internal shells of Sepia, (Onychoteuthis) in the Lias of Culmbach and Banz.
ExPLANATION OF PLATE 31. 53
the siphuncle is laid bare at a. b. c. d. At e, e, and from thence inwards, it is covered by a soft calcareous coating or sheath.
. Collar, projecting inwards from the transverse plates,
and supporting the Siphuncle. See Note, V. I. p. 243.
. 2. Upper horny mandible of the animal, with a hard
calcareous point. (Owen.) :
. 3. Lower horny mandible, armed with a similar cal
careous point. (Owen.)
. 4. Calcareous point, and palate of upper mandible
separated from the horny portion. (Owen.)
. 5. Under surface, or palate of a Rhyncholite, or fossil
beak, from the Lias at Lyme Regis, analogous to the recent specimen, fig. 4. (Original.)
. 6. Upper view of another Rhyncholite from the same
stratum and place. Black portions of the horny
a double keel-shaped indented process, enlarging from its apex backwards.” (Original.)
PLATE 32. V. I. p. 244.
1. Part of the petrified shell, and casts of the intérior of some of the chambers, of a Nautilus hexagonus, from Marcham, Berks. This fossil exhibits at its smaller End, from d to b., a series of casts of the Air chambers, from which the external shell has been removed. The cavity of each chamber is filled with a disc of pure calcareous spar, representing the exact form of the chamber into which it had been infiltrated. In the larger portion of this fossil, the petrified shell retains its natural place, and exhibits fine wavy lines of growth forming minute Ribs across its surface. (Original.)
2. Fractured shell of N. hexagonus, from the Calcareous grit of Marcham. The chambers are lined with calcareous spar, and a circular plate of the same spar is crystallized around the siphon. The interior of the siphon is filled with a cast of Calcareous grit, similar to that which forms the rock from which the shell was taken. See V. I. p. 247.f. (Ori
* Although the resemblances between these fossil beaks, and that of the animal inhabiting the N. Pompilius, are such as to leave no doubt that Rhyncholites are derived from some kind or other of Cephalopod, yet, as they are found insulated in strata of Muschel kalk and Lias, wherein there occur also the remains of Sepia that had no external shells, we have not yet sufficient evidence to enable us to distinguish between the Rhyncholites derived from naked Sepia, and those from Cephalopods that were connected with chambered shells. Lyme Regis, in which the external open chamber contains a Rhyncholite.
# This fossil exhibits the Siphuncle in its proper place, passing
I possess a specimen of a fossil Nautilus from the Lias at
EXPLANATION OF PLATE 32. 55
Fig. 3. represents in its natural size, a portion of the Siphuncle which in Fig. 2, is laid bare along its course through the chambers, d. e. f. In the transverse Plate, h, the siphuncular collar is entire, but a Section of another collar in the transverse Plate, i, shows the contraction of the Siphon at its passage through this aperture, and exhibits also the overlapping, or squamous suture by which the Collar is fitted to the superior and inferior portions of the calcareous Sheath of the Siphon. See V. I. pp. 247, 248. Note. (Original.) A similar structure may be seen at the Collars of the transverse Plates of the N. Striatus. See Pl. 33.
across the cavities of the Air chambers. As in the recent Nautilus Pompilius, there is no communication between the interior of the Siphon and that of the Air chambers, so in this fossil shell, there is proof that no communication existed between these cavities. A transverse section at a. shows the thin edge of the sheath of the siphuncle, surrounded externally with calcareous spar, and filled internally with Grit. Other Sections of the Siphuncle at b. d. e. f. show the calcareous Grit within its cavities to be contracted at its passage through the collars of the transverse plates, and most enlarged midway between one transverse plate and another.
This fossil affords two proofs that no communication existed between the interior of the Siphuncle and that of the Air chambers. 1st, the . calcareous sheath of the Siphuncle is seen at d. e. f. completely en- a closing the calcareous grit which forms the cast within it. 2dly, had there been any communication between the interior of the siphuncle, and that of the air chambers, these chambers must have received some portion of the materials of the grit that have filled this Siphuncle: not a particle of grit is found in any one of the adjacent air chambers, but they are all lined, and some of them nearly filled with a crystalline. deposite of Carbonate of Lime, disposed in uniform plates around the interior of each chamber, and around the Siphuncle. See Fig. 2. c. c1. a. a. a. ao. and Fig. 3. d-k. This deposite can only have been formed from water charged with carbonate of lime, introduced by infiltration, after the interment of the shell, and filling the chambers which are thus uniformly invested.