TURRILITES.
Turrilites. [Lign. 163].—Shell spiral, more or less conical, coiled obliquely round an axis, and turriculated. Spire sinistral, whorls contiguous, apparent, with a perforated umbilicus. Edges of septa very sinuous. Siphuncle continuous, situated either on the external convexity, or near the suture at the base of the wreath.
The discovery of three species of these elegant shells rewarded my researches in the little marl-pit at Hamsey, already noticed, and were the first examples of the genus found in England.[423] Like the Ammonites, Scaphites, Hamites, &c. with which they are associated, the Turrilites of our Chalk-marl seldom possess any traces of their shells. The specimens are solid and tolerably sharp casts, with occasional indications of the septa, and more rarely of the siphunculus. They vary in size from two or three inches to two feet in length; and are frequently more or less elliptical, from compression. The three species which generally occur in the Sussex and Kentish chalk, are T. costatus, [Lign. 163], fig. 2; T. tuberculatus (Foss. South D. pl. xxiv. fig. 7), characterised by its four rows of tubercles; and T. undulatus (Foss. South D. pl. xxiv. fig. 8), the wreaths of which are ornamented with plain, slightly undulated, transverse ribs. These are all reversed, or sinistral shells; that is, the spire is twisted to the left, the aperture being on the right hand of the observer when the shell is placed on its apex, as in fig. 1. Several other species of Turrilites occur in the Chalk of France,[424] one of which, T. catenatus, is represented [Lign. 163], fig. 1.
[423] Sow. Min. Conch, tab. xxxvi.
[424] See M. D’Orbigny’s Paléontologie Française.
Some of the Turrilites attain a considerable magnitude. The largest found in England is a specimen of T. tuberculatus (Min. Conch. tab. lxxiv.), from Middleham, in the parish of Ringmer, near Lewes; when perfect, it must have been full two feet in length: it consists of six wreaths, the siphuncle, in the state of pyrites, appearing in three or four; portions of the nacreous internal layer of the shell remain.[425] In some specimens in my possession, the form of the aperture, and the termination of the columella, are distinctly shown; as in the fine example the last whorl of which is represented in [Lign. 164].
[425] This specimen is now in the British Museum.
Lign. 164. Turrilites tuberculatus, (Bosc.) nat.