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XXXII.—Letter from MR. JAMES DE CARLE SOWERBY to the Secretary, on the Genus Crioceratites and on Scaphites Gigas.

[Read March 8th, 1837.] DEAR SIR, THE recent discovery in the Isle of Wight, by Mr. Bowerbank, of a fossil shell resembling Ammonites, but differing essentially from that genus, and of a magnificent Scaphites, appears to me of sufficient importance to be laid before the Geological Society ; I have, therefore, drawn up the following descriptions, accompanied by reduced figures of the fossils*. PI. XXXIV.

CRIOCERATITES.

Generic Characters.—An involuted chambered shell, with sinuated septa ; the whorls free, sometimes very distant. Siphon in the external margin of the septum. The genus is distinguished from Ammonites by the whorls not uniting or closing upon one another, or making even an impression, except towards the centre of the disc, and not there in all species. From Scaphites it also differs in not having the last whorl produced and bent like a hook ; this whorl is often marked differently from those which precede it in both genera. Many of tbe shells to be grouped in this genus have hitherto been considered Hamites. The species to which I allude are Hamites Beanii, H.plicatilis, and H. intermedins^, of Phillips (Geol. Yorks., Pt. I, PI. 1., figs. 28, 29, 22.), Hamites rotundus, (Min.Con., PI. 61.), H. spinulosus, H. spiniger, H. tuber- culatus, H.nodosus, and H. turgidus, of Mineral Conchology (PI. 216.).

• These fossils I was induced to consider as belonging to an undescribed genus, for which I proposed, in my communication to the Society, the name of Tropceum: since that notice was read, I have seen in the second part of the second volume of Memoirs of the Geological Society of France, published in March, 1837, M. le Ch. Leveille's description of his new genus Crioceratites, which proves to be identical with Tropceum. As M. Leveille's paper must have been read before my letter, it is clear that the name Crioceratites must be employed in place of Tropceum, and it is a very good name. The circumstance of a foreign author having distinguished the genus goes far to prove the propriety of its being established. Two of Leveille's species occur in the Speeton Clay of Yorkshire. One of them, C.Emeritii (Loc. Cita. PI. XXIIL, f. 1.), is Hamites Beanii, of Phillips, PI. I., f. 28, the other, C. Honoratii (Loc. Cita. PI. XXII., f. 2), is not yet published by any English author, but has been called H. plicatilis, although distinct from the species so named in the Mineral Conchology (PI. 234.).—Dec. 1837. •f- I strongly suspect this is not H. intermedins of Min. Conch. (PI. 62.) Downloaded from http://trn.lyellcollection.org/ at University of St Andrews on March 23, 2015

410 Mr. J. DE C. SOWERBY on the Genus Crioceratites

If we arrange the genera of concamerated cephalopods, furnished with a siphon, and with sinuated edges to their septa, according to the straightness or degree of curvature of the shell, we shall have them in the following order, beginning with that which has no curve: Baculites. Hamites. Crioceratites. Scaphites. Turrilites. Ammonites. A similar series may be formed of those which have entire edges to the septa: Belemnites. Orthoceras. Phragmoceras. £ pirula. 1 ituites. Nautilus. And if we reverse the second of these groups, the genus Goniatites will be found a natural link between them. The genus Crioceratites fills up between Hamites and Scaphites, just where it was wanted, parallel to Spirula*. The gigantic species from the Isle of Wight I shall name, after its for­ tunate discoverer, Crioceratites BowerbanJcii, PL XXXIV., fig. 1. SPEC. CHAR.—Whorls about four, slightly flattened on their sides, and nearly close; the inner ones ornamented with numerous radiating furrows, which, gradually disappearing upon the outer whorl, are replaced by eight or ten thick, arched costae, extending completely across the whorl, and largest and most elevated towards the thinly edged, transversely oblong aperture. The septa are rather distant, terminating where the costae begin to enlarge. There is generally a short rib almost close to the aperture, and in one speci­ men I have noticed an additional short rib between the two long ones which precede the termination. In an individual sixteen inches wide, the septa are one inch and a half apart. This fossil occurs in the lower green sand on the south coast of the Isle of Wight.

* I have seen the drawing of a fossil found in Devonshire by Mr. Austen, of a form similar to that of Turrilites> but with entire edges to the septa; its situation would be between Lituites and Nautilus. Downloaded from http://trn.lyellcollection.org/ at University of St Andrews on March 23, 2015

and on Scaphites Gigas. 411

The Scaphites obtained by Mr. Bowerbank is the Hamites Gigas of Mineral Conchology, t. 593, which must now be called Scaphites Gigas, (see PI. XXXIV. fig. 2.) The involute portion resembles the inner whorls of the shell just described, but it is upon the straight portion only that the large ribs appear, which moreover have three knobs upon each. This is the third species of large Scaphites which has fallen under my notice. I have seen several portions similar to the figure in Mineral Conchology, mostly found near Maidstone, but this is the only specimen showing the involute com­ mencement which I have met with, and I for some time considered it to be an undescribed species. I remain, dear Sir, Your obedient servant,

J. D. C. SOWERBY. January 18th, 1837.

VOL. V. SECOND SERIES. 3 H Downloaded from http://trn.lyellcollection.org/ at University of St Andrews on March 23, 2015