NATJTILID^. 
245 
1854. Xautilus Farrinf/doaeiisis, Morris, Catalogue of British Fossils, 
2nd ed. p. 306. 
1858. Xautilus undulatus, Ooster, Catalogue des Ceplialopodes Fossiles 
des Alpes Suisses, pt. iii. p. 15. 
1859. Xautilus Farringdonensis, Pictet et Campiche, Description des 
Fossiles du Terrain Cretace des Environs de Sainte-Croix (Paleont. 
Suisse), ser. ii. pt. i. p. 123. 
1862. Xautilus undulatus, Bristow and Etheridge, in Bristow’s Geology 
of the Isle of Wight (Mem. Geol. Surv. of Great Britain, Sheet 10), 
p. 137. 
y 1863. Xautilus undulatus, Schafhautl, Siid-Bayerns Leth. Geogn. 
“ Der Kressenberg und die siidlich von ihm gelegenen Hochalpen” 
kc. p. 216, Taf. liii. f. 9. 
1871. Xautilus Faring donensis, Phillips, Geology of Oxford and the 
V^alley of the Thames, p. 441. 
Char. “ Shell when young smooth and regular, with flatfish 
sides, a broad rounded back, and semi-oval aperture ; when about 
two inches in diameter it enlarges rapidly, expands at the sides, and 
begins to undulate over the back ; when adult, the whole shell is 
ribbed in broad coarse undulations, which are deepest on the baek, 
but ill-deflned on the sides ; back marked by a line at first slightly 
raised, which in the old shell forms a ridge between the undulations ; 
umbilicus covered ; septa flexuous ; siphuncle near the ventral 
[inner] margin.” {Sharpe.) 
Remarlcs. Sowerby describes the septa of this species as being 
somewhat numerous, each one . . . crossed obliquely by an 
undulation of the surface.” 
Sharpe observes that he only saw one specimen of this species 
from the Chalk ; a young shell, 2| inches in diameter and inch 
broad at the mouth.” He adds : — This shell is found more plenti- 
fully in the upper part of the Lower Greensand, where it reaches a 
diameter of 4 or 5 inches. . . . When young, N. undulatus has con- 
siderable resemblance to X. LargilUertianus [d’Orb.^], from which 
it is distinguished by its closed umbilicus ; in its undulated stage it 
cannot be confounded with any other species.” 
Though Sowerby’s type is not in the British Museum, there is a 
specimen labelled “ Nautilus undulatus, M. C. 182,” in his hand- 
writing, which is clearly identical with his species as described in 
the ‘ Mineral Conchology.’ 
Two specimens from the Lower Greensand of Hythe and Lympne 
in Kent, though badly preserved, show distinctly the strong undu- 
lations characteristic of this species, and the test exhibits also strong 
1 Pal. Fran^., Terr. Chet. 1840, vol. i. p. 86, pi. xviii. 
