46 KOCENE MOLLUSCA. 
No. 8. NAUTILUS REGALIS. Sowerby. Tab. IV. 
NaUTILUs REGALIS. J. Sow. 1823. Min. Con. vol. iv, p. 77, pl. 355. 
— _ Def. 1825. Dict. des Se. Nat. vol. xxxiv, p. 300. 
— — Weth. 1836. Philos. Mag. and Journ. yol. ix, p. 465. 
_ — Morris. 1843. Cat. Brit. Foss. p. 183. 
— — Pictet. 1845. Traité élément. de Paléont. vol. ii, p. 338. 
a — Sow. 1849. Dixon’s Geol. Hist. &c. p. 120. 
NV. Testa levigatd, sub-ventricosd, in aspectu ventrali compressa, obscure undulata ; 
apertura obtuse-ellipticd ; umbilicis obtectis ; septis simplicibus, concavis, utroque latere 
perparum undulatis, siphone sub-centrali perforatis ; lobis dorsalibus brevibus, rotundatis, 
haud refleais. 
The present species is distinguishable from the preceding by the closed umbilicus, 
and by its general form, which is less ventricose than that of JV. centralis. It is a 
smooth shell, flattened on the sides, and bluntly rounded, and obscurely undulated 
on the ventral aspect. The aperture presents a subquadrate appearance. The 
umbilicus is closed by a thickening of the lip, assuming the appearance of a solid 
axis to the shell. The septa are nearly simple, presenting on each side slight undu- 
lations, and the short, rounded dorsal lobes are deeply concave, and not reflected. In 
the young shell the septum is characterised by a conical depression placed on the 
dorsal margin close to the preceding whorl; as the shell enlarges this gradually 
decreases in size and depth, and ultimately disappears. It was of course moulded on 
a corresponding protuberance on the animal, probably an enlargement of the epithelial 
cincture. In some species the cavity is very deep. It was on this character that 
De Montfort, mistaking the depression for the mouth of a second siphuncle, founded 
his genus Bisiphites. The siphuncle is small and excentric. The lines of growth, 
like those of the preceding species, are decussated, and reflected backwards in broad 
undulations. 
The Nautilus regalis attained a large size. The specimen figured, for the use of 
which I am indebted to Mr. Dixon, measures 9°5 in. in diameter, by 5 in. across. The 
species occurs at Islington, Regent’s Park, Chalk Farm, Hyde Park, and at Bognor. 
It appears to have been one of the most common of the English Kocene Nautili. The 
septum is represented at Tab. VIII, fig. 5. 
No. 9. NAvTILUS URBANUS. Sowerby. Tab. III, fig. 2 a—é. 
NAUTILUS URBANUS. J.D. C. Sowerby. 1843. Min. Con. vol. vii, p. 36, pl. 628. 
_ = Morris. 1843. Cat. Brit. Foss. p. 183. 
— — Pictet. 1845. Traité élement. de Paléont. vol. ii, p. 338. 
NV. Testd discoided, in aspectu ventrali rotundatd, et obscuré undulata ; umbilicata ; 
apertura subquadratd, elongatd ; septis oblongis, concavis, in utroque latere leniter undulatis 
et siphone excentrico perforatis ; lobis dorsalibus perbrevibus, oblique truncatis, haud reflexis. 
