Lign. 151. Nautilus elegans.
Lower Chalk. Lewes. (1/6 nat. size.)
In the White Chalk near Lewes, casts of several very large Nautili have been found; but shells of this genus are more abundant in the lower division, the Chalk-marl. A large and beautiful species, Nautilus elegans (Min. Conch. tab. 116), is not unusual in the marl-pits near Lewes, Clayton, Steyning, &c. and may be considered as characteristic of that portion of the Cretaceous deposits. The first specimen discovered (Foss. South D. tab. xx) was from the marl-bank immediately at the foot of the mound on which stands the church of Hamsey, a little hamlet on the north of Lewes; a spot from which I obtained numerous other cephalopodous shells, at that time unknown as British species. The collocation of fossils at Hamsey is similar to that observable in the quarries at St. Catherine’s Mount, near Rouen. These remains only occur as casts, no vestige of the shell remaining; but sections will sometimes show the situation of the siphon, its tube being filled with a different material from that which occupies the cells. This is exemplified in the section of a smaller species (N. pseudo-elegans, [Lign. 150], fig. 2), in which the channel of the siphon is filled with a dark-coloured marl, a; the lines formed by the section of the smooth septa are also shown. In the same lignograph, fig. 3, a front view and profile of another chalk-marl Nautilite are figured.[411]
[411] The student will find a section of the shell of the recent Nautilus a very instructive object of comparison, in the investigation of the fossils of this family.
Lign. 152. Nautilus Saxbyi. Lower Greensand.
In the Chalk, as well as in many other calcareous deposits, the shells of the Nautili, Ammonites, &c. are very rarely preserved; even the internal septa are often dissolved, and the stony casts, moulded in the cells, remain distinct, and readily separate ([Lign. 153]). An entire series, from the innermost cell to the outer chamber, may sometimes be obtained (in the Coralline Oolite); forming, as it were, a dissected model of the internal structure.[412] The beaks or mandibles are occasionally found fossil ([Lign. 150], fig. 1).
[412] Bd. pl. xlii. fig. 1: see also plates xxxi. to xliii., for illustrations of Nautilites.