J Basire, Zincog.

In neither of the above described specimens of Belemnite having the soft parts and phragmocone in natural connections, is there any evidence of the muscular part of the mantle having been continued over the capsule of the phragmocone; it is traceable for a short way below the peristome in Mr. CUNNINGTON'S specimen*; but it is best developed where it surrounded the compressible part of the body of the Belemnite anterior to the shell. There seems no reason, however, to doubt that the skin, which, in existing naked Cephalopods is thin and lubricous, and more easily detached from the subjacent muscular layer than in the lower Mollusks, was extended over that part of the phragmocone extending beyond the alveolus, as there has been already shown evidence of its continuation over the alveolar and solid part of the spathose guard: its gelatinous base was less favourable for preservation than the fibrinous nature of the muscular tunic, and its destruction is, therefore, not surprising. The dark stain upon the clayey matrix, which usually extends a little beyond the preserved muscular structure, may in part be due to the pigmental cells of the skin; and these seem evidently to have produced the thin crust of a dark greenish colour which hides part of the fibrous layer of the mantle in the third specimen left for description.

This, which is from the collection of Mr. PRATT, is chiefly remarkable and valuable for the perfect conservation of the complex muscular structures of the head and its uncinated arms. Eight of these, forming the normal series of cephalic arms, may be defined, radiating from a contracted base. In this base may be observed two decussating groups of curved fibres (h), the posterior one with its concavity turned towards the mantle, the anterior one with its concavity directed forwards, and its horns continued into the bases of the arms. A similar decussated arrangement of fibres exists in the Onychoteuthis, and is described and figured by CUVIER in the corresponding part of the head of the Octopus. Almost the entire extent of five of the cephalic arms is preserved, as shown in the figure; they are rather longer in comparison with the mantle than in the modern Onychoteuthis, but not as compared with the entire body of the Belemnite when this is lengthened out by the terminal spathose guard: the longitudinal arrangement of the fasciculi of muscular fibres of the arms is very distinct.

I placed a portion of the muscular tissue under the microscope, and succeeded by the aid of a drop of diluted acetic acid in softening and unravelling the constituent fibres; they presented the same size as the fibres from the corresponding part of one of the arms of an Onychoteuthis, but the faint transverse striæ visible in the recent fibre§ had disappeared in the fossil, and only an obscure granular structure

could be discerned.

Each of the arms seems to have been provided with from fifteen to twenty pairs of hooks, which were doubtless developed from the horny hoops which encircled the caruncles of the acetabula, as in the modern Onychoteuthis.

*Pl. VI. fig. 1, d.

+ Pl. V.

Pl. VII. fig. 4.
Pl. VI. fig. 2, is a magnified view of the most perfect of these hooks.

§ Ib. fig. 3.

Two small protuberances at the origin of the normal brachia are the only parts which represent the bases of the pair of long tentacula, superadded to the eight shorter arms in the existing Decapoda.

On each side of the head, behind the bases of the arms, there is a convex protuberance formed by a well-defined semicircular band, about a line in thickness, of grey fibrous matter, the fibres or layers being parallel with the curve of the band. These parts are more distinctly shown in Mr. CUNNINGTON'S specimen, in the description of which the reasons for regarding them as belonging to organs of vision are given. In the present specimen they indicate, according to this view of their nature, that the eye-balls of the Belemnite were sessile*, and agreed in size, as in position, with those of the modern naked Cephalopods.

Another specimen of similar size, in the collection of Mr. PRATT, exhibits the upper two-thirds of the visceral cavity formed by the mantle and the head with the bases of the arms, one of which is preserved to the extent of two inches, another to that of one inch, and on both these a few of the horny hooks remain. At the lower part of the head a circular amorphous granular mass is visible; it is bounded anteriorly by a curved fasciculus of fibres with the concavity directed backwards: above these the fibres which are continued into the bases of the arms commence from a fasciculus curving in a direction opposite to the preceding. These decussating bands are similar to those in the former specimen but are more strongly marked. The fibres continued into the arms are chiefly longitudinal. The few hooks which are preserved in this specimen are identical in size and shape with the more perfect series in the preceding specimen.

There is a minute trace on the left side, near the lower end of the specimen, of an obliquely striated horny plate. Most of the preserved fibrous structure of the flattened mantle is transversely arranged, as in all the other specimens; but a faint trace of longitudinal or retractile fibres may be discerned near the anterior margin of the mantle.

The fracture of the slabs of clay containing the last two instructive specimens has crossed obliquely that part of the abdomen in which is situated the striated thin horny plate, agreeing with that which I have ascribed to the gizzard: wanting therefore both the ink-bag and phragmocone, these specimens were defective in the requisite evidence to associate the uncinated arms with the complex shell, muscular mantle, and rounded fins of the Belemnites.

The coexistence with the true Belemnites, in the Oxford clay at Christian-Malford, of fossil Calamaries with a dorsal horny gladius or pen, like those from the lias at Lyme Regis described by Dr. BUCKLAND, made it still more desirable to obtain such evidence as could only be given by more entire specimens of those ancient uncinated Cephalopods than those above described from the collection of Mr. PRATT, which were the first and for some time the only specimens of the kind that I had seen. The subsequent fortunate discovery of the unique example submitted to my ex* In the Nautilus the eyes are pedunculated. † Bridgewater Treatise, i. p. 308. # Pl. III.