DIBRANCHIATA.
(Cuttle-fishes.) Of the two great divisions of cephalopodous Mollusca, that which is represented at the present day by the pearly Nautilus was developed in the greatest profusion and variety in the palEeozoic and secondary periods ; whilst the more active and intelligent cuttle-fishes and squids have not been (certainly) found in rocks older than the liar, and scarcely above 100 are found in the whole secondary and tertiary series, while twice as many have been obtained in existing seas.
The Sepiacice are represented in the middle and upper oolites by the genus Coccoteuthis (fig. 22, 6), whose strong and granulated bone is furnished with broader lateral expansions than the recent cuttle-fishes. In the older tertiaries of London and Paris, many species of Sepia appear to have existed, but only the solid muero (fig. 22, s) of the shell is usually pre served. In the miocene tertiary of Malta, a diminutive cuttle-bone is not rare ; and at Turin a remarkable form (Spirulirostra, fig. 22, 7) has been discovered, in which the apex is provided with a chambered and siphonated cavity like the shell of the Spirula,. Two other genera, Belaptera (fig. 22, s) and Belemnoris, very imperfectly known by rare and fragmentary examples, occur in the eocene tertiary.
Remains of the Calamaries (Teuthiclee) are often found in the fine-grained and laminated argillaceous limestones of the has and Oxford clays, as at Lyme Regis, and Boll of Solenhofen. Some of these are slender, like the pens of the recent Omma strephes, and furnished with a small conical appendix, as in that genus ; whilst others are broad, and pointed at each end (Beloteuthis). The most common form has the shaft wide and longer than the wings, and is truncated posteriorly. It has a nacreous lining, and is usually accompanied by a large and well-preserved ink-bag (fig. 22, 4). These were called Belemnosepia by Agassiz and Buckland, who supposed them to belong to the same animal with the Belemnite. They have
also been called Longo-sepia and Loliginite,s ; but the name Geoteuthis, given by Count Munster, appears less objection able. One species (Mastigophora is of frequent occurrence in the Oxford clay near Chippenham, which retains not only the horny (chitinous) pen and ink-bag, but also the muscular mantle, the rhombic terminal fins, and at least the bases of the arms, with the minute hooks, and traces of the mandibles. Horny claws, like those of the uncinated Calamary (Onych,oteuthis), have been observed arranged in double series in the liar of Watchett, and they sometimes occur in great numbers in the coprolitic remains of the Emilio sauri. The most remarkable examples of this kind are pre served in the lithographic limestones of Solenhofen, and show that the extinct Calamary had ten nearly equal arms, the tentacles, in their retracted condition, being undistinguish able from the rest—each furnished with 20 to 30 pairs of formidable hooks. What further evidence was needed respecting the nature of this creature has been supplied by the Chippenham fossils, which in all probability are iden tical in genus, if not in species, with the Acanthoteuthis described by Minster. One of these extraordinary fossils— the mummy of a cuttlefish more ancient than the chalk for mation and the upper oolites—is represented in (fig. 22, 2,) reduced to one-sixth from the original in the British Museum. Nine of the arms are preserved, the sclerotic plates of the eyes, the bases of the large lateral fins, the small ink-bag, and the conical shell. This shell, which is chambered internally, like the phragmocone of the Belemnite (fig. 22, 1), has an outer sheath of fibrous structure, one-fourth of an inch thick at the z. Belemnites Oweni ; Oxford Clay, Chippenham. p. Phragnsocone exposed by the removal of the fibrous guard from one side ; e, septum, showing the marginal eiphunde.
a. Acanthoteuthis antigun' (Cunnington) Oxford Clay, Chippenham ; dorsal aspect.