NOTES ON THE CAMBRIDGE. GREENSAND. 489
the pinched-up back ; this character is very conspicuous in the inner whorl, but becomes gradually less in the later chambers.
The species was found by Leymerie in the Gault of the Departe- ment de PAube ; but I have not seen it quoted from any other locality.
Nautllcis dosqualis, Sow.
Nautilus incequalis, Sow. Min. Conch, pi. lx. lower figs. Nautilus Clementinus (?), Pict. & Camp. Ste. Croix, vol. i. pi. xix. fig. 1-5 (nee D'Orb).
If the figure and description of M. d'Orbigny's Nautilus clemen- tinus be compared with those of Pictet and Campiche, I think it will be evident that the two are really different species, supposing, of course, that the figures are correct representations of the original specimens. This can only be decided by an inspection of the types, which I have not had an opportunity of making ; it is remarkable, however, that both the figured forms appear to be represented among the Cambridge Nautili. Those agreeing with the N. Clementinus of D'Orbigny are large and somewhat compressed, oblong in cross section, not inflated, but rather flattened near the umbilicus, which is small. Those resembling the figure of Pietet and Campiche are more inflated, and broader in proportion to their length, with a larger umbilicus bordered by a low keel (which, however, is not so marked as in N. expansus) ; the siphuncle is situated close to the inner edge of the chamber. Both forms have numerous close-set chambers, about 16 being visible ; but the latter does not appear to attain so large a size as the true N. Clementinus.
The smaller and more inflated form certainly appears to exist in the Folkestone Gault, and when obtained thence has, I believe, been usually referred to the N incequalis of Sowerby, with the meagre description and poor figures of which it sufficiently agrees. If, therefore, I am correct in the above surmises, the N. Clementinus of Pictet and Camp, becomes a synonym of N. incequalis, Sow. The inequality of the chambers in the young shell, and the increasing propinquity of the septa being, however, the ordinary mode of growth in the genus, its designation seems rather meaningless.
Nautilus n. sp.
Cast oblong, umbilicated, chambers few, only 12 being generally visible, and the last ones being as high as they are wide ; the septa are consequently wide apart, sinuate and bent back near the umbilicus ; siphuncle situated outside the centre and about one third of the distance from the outer edge.
This is the commonest form of Nautilus among the Cambridge coprolites, but does not seem to agree with any previously described. Casts of the umbilicus seem to indicate that the shell had faint longitudinal striae crossed by the lines of growth. Until, however, the shell has been found and the Nautili of the Gault more thoroughly investigated, it will be safer not to give a name to the above- described casts.
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