Fig. l. Represents the common calmar or squid (Loligo vulgaris, Lam. Sepia loligo, Linn.) shewing the place and excretory duct of its Ink bag, and the position of the feet on the anterior margin of the head. (Blainville.)

Fig. 2. Side view of the Pen of the Loligo vulgaris, shewing its position in the back of the animal, fig. 1. (Original.)

Fig. 3. Concave under surface of the same pen. (Original.) [049]

Fig. 4. Convex upper surface of portion of another recent pen, of the same kind. The structure of figs. 3 and 4 closely resembles that of the fossil species represented at fig. 6, of this same Plate, and also at Pl. 29. fig. l. and Pl. 30. In all of them, the horny plates are composed of a series of longitudinal fibres, intersected by another series of transverse fibres. The disposition of the transverse fibres is most simple in the recent species; passing obliquely outwards from each side of the central shaft, like the barbs or fibrils in the vane of a feather, and being most distinct towards the outer margin.
The longitudinal fibres are scarcely visible in the recent species, except where they are collected into fluted fasciculi, (Pl. 28. fig. 4. BB.) in those parts which correspond with the marginal bands of the fossil species. (Original.)

C. Central part of the Pen, raised like the shaft of a quill between its fibrils.

Fig. 5. Ink bag of a recent Cuttle fish, dissected by the author at Lyme Regis, 1829, containing its natural Ink in a desiccated state; it is a black shining Jet-like substance, having a splintery fracture, and resembling the substance and fracture of the fossil Ink. Its bulk is not much reduced by desiccation. (Original.)

Fig. 6. Upper convex surface of a fossil pen of Loligo Aalensis from the Lias of Lyme Regis. A. A. the barbs; B. B. the marginal bands; C. axis of the shaft; D. Excretory duct of the Ink bag, distended with petrified Ink.* (Original.) [050]

Fig. 7. Upper surface of Fossil Loligo from the Lias of Lyme Regis. A, A, Barbs of the Pen. B, B, Marginal bands. C, Axis of the Pen.

d, upper plate of marginal band, having an unusually corrugated surface, which may be the result of imperfect growth of the transverse fibres; if fully expanded they would probably have resembled those of the subjacent Plate at d''. (Original.)

d'. Magnified representation of the rugous surface of d.

d'''. Magnified representation of the second plate of the marginal band, Fig. 7. d''.

e. Upper surface of second Plate of the shaft of the pen; here the transverse wavy lines predominate over the vertical straight lines; but both are visible.

f. Upper surface of third plate; here the vertical straight fibres prevail over the transverse wavy fibres.

* In this specimen we see distinctly the disposition of the marginal bands.