EXPLANATION OF PLATES 28
49
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. 1. 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 the 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.[1] (Original.)
- ↑ In this specimen we see distinctly the disposition of the marginal bands.
