Nautilus. 
MOLLUSCA. 
05 
Geology and Mineralogy Considered, I. p. 359, and II. p. 63, 
pi. 43, figs. 3 and 4. 
Involute ; sides somewhat flattened ; inner volutions 
entirely concealed ; aperture bluntly triangular ; siphuncle 
placed nearest to the inside ; septa concave, greatly recurved 
at their extremities, and with a deep indentation in the edge 
on each side, producing a zigzag appearance; thickness 
about a third of its diameter. 
Found in the Clay at Ilighgate, in London. 
24. N. striatus. — The Striated Nautilus, pi. XXIV. 
fig. 4. 
Nautilus striatus. Sowerby, Min. Conch. II. p. 183, pi. 182. 
Fleming, Brit. An. p. 230. De la Beche, Geo. Manuel, 
p. 369. 
Discoidal, somewhat gibbose, the inner volutions few, 
entirely concealed, and increasing rapidly ; sides covered 
with extremely strong, elevated, numerous, irregular, concen¬ 
tric striae, and having almost the appearance of ridges ; 
umbilicus large, but not deep, in which the edges of the inner 
volutions are slightly indicated; ambit compressed ; aperture 
almost orbicular, a little flattened on the back, and equal 
to about half the diameter of the disk ; greatest diameter 
about eight inches. 
Found not unfrequently in the Lias at Lyme Regis, Dor¬ 
setshire. 
25. N. imperialism —The Imperial Nautilus, pi. XXIV. 
fig. 5. 
Nautilus imperialism Sowerby, Min. Conch. I. p. 9. Fleming, 
Brit. An. p. 229. 
Discoidal, umbilicate ; inner volutions wholly concealed ; 
sides gibbose and smooth, but striated concentrically in the 
young state ; aperture lunate, with blunted sides ; siphuncle 
placed nearest in the inside ; septa entire, concave, broadest 
in the centre, truncated and a little recurved at their ends; 
umbilicus pretty large, but not deep. 
This is a widely diffused species, and is found in the Clay 
at Highgate, near Munster, Island of Sheppey, Brentford, 
Suffolk, Middlesex, Essex, Berkshire, Hampshire, Wiltshire, 
Surrey, and Kent. 
In some specimens the outer coating is of a light, chestnut- 
brown colour, especially in young shells, beneath which the 
shell is of a fine pearlaceous lustre ; it is also nacred within. 
26. N. bilobatus. —The Two-lobed Nautilus, pi. XXIV. 
fig. 6. 
Nautilus bilobatus. Sowerby, Min. Conch. III. p. 89, pi. 
249, fig. 2, 3. Fleming, Brit. An. p. 230. 
Subglobose, umbilicate ; inner volutions entirely con¬ 
cealed ; sides smooth ; back slightly flattened ; umbilicus very 
small, and nearly cylindrical in form ; aperture transversely 
elongated, its width being nearly four times its length ; 
siphuncle almost central, on each side of which the septa are 
very concave, forming two elliptical lobes ; thickness and 
width about equal. 
Found at Closeburn, Dumfriesshire, in the Red Limestone, 
on the property of C. G. S. Menteith, Esq, 
27. N. intermedius. — The Intermediate Nautilus, pi. 
XXIV. fig. 7. 
Nautilus intermedius. Sowerby, Min. Conch. II. p. 53, 
pi. 125. Fleming, Brit. An. p. 230. Dc la Beche, Geo. 
Manuel, p. 369. 
Globose, umbilicate; inner volutions about half exposed, 
and increasing rapidly; sides somewhat depressed, concentri¬ 
cally striated ; ambit broad flattened ; aperture a little quad¬ 
rangular ; siphuncle round, placed nearest the external mar¬ 
gin ; septa numerous. 
Found at Keynsham, in FYrruginous Limestone, and at 
Castle Hedingham, Essex. This species is nearl} allied to 
the following, but is distinguished by not being so thick as 
the obesus , and the septa are not so numerous. The striae 
mentioned are not, however, discernible, except when the 
outer coating is removed. But the circular form of the 
siphuncle at once distinguishes it from that of the obesus , 
which is transversely oval. 
28. N. obesus. — The Swollen Nautilus, pi. XXIV. 
fig. 8. 
Nautilus obesus. Sowerby, Min. Conch. II. p. 51, pi. 124. 
Fleming, Brit. An. p. 230. De la Beche, Geo. Manuel, 
p. 369. 
Gibbose, umbilicate; inner volutions entirely concealed; 
sides plain ; ambit broad and flat; aperture very large, some¬ 
what quadrangular, its length being two-thirds the diameter 
of the disk ; siphuncle oblong-ovate, transverse, and almost 
central ; septa very numerous, but not recurved, which pro¬ 
duces an open form to the umbilicus, which is pretty large, 
but not deep ; greatest diameter thirteen inches. 
Discovered in Ferruginous Limestone at Norton-Under¬ 
ham by Mr Strangcways. 
Distinguished from N. intermedius by its transversely oval 
siphuncle, which inclines inwards, and in the umbilicus 
exhibiting no indications of the inner volutions. 
29. N. complanatus. —The Flattened Nautilus, pi. XXIV. 
fig. 9. 
Nautilus complanatus. Sowerby, Min. Conch. III. p. 109, 
pi. 261. Fleming, Brit. An. p 231. De la Beche, Geo- 
Manuel, p. 464. 
Discoidal compressed, with four or five volutions; the 
inner ones completely exposed ; their inner edges flattened, 
leaving a concave surface ; half of the last volution is desti¬ 
tute of septa; sides flat and smooth ; aperture lanceolate, its 
length being nearly equal to six times its width; near the 
inner angle, the edge of each septum is provided with a 
reversed sinus; ambit rounded. 
Discovered at Scarlet, Isle of Man, by J. S. Ilenslow, Esq. 
in the Slaty Limestone. 
30. N. tuberculatus. — The Tuberculated Nautilus, pi. 
XXIV. fig. 10. 
Nautilus tuberculatus. Sowerby, Min. Conch. III. p. 90, 
pi. 249, fig* 4. Fleming, Brit. An. p. 230. 
Discoidal, thick, very largely umbilicate ; the inner volu¬ 
tions almost wholly exposed ; outer volutions thick, the inner 
ones progressively descending to a deep umbilicus, the shape 
of a reversed cone; at about a third of the breadth of the volu¬ 
tions, is situated a series of large round tubercles, which are 
prolonged to the inner margins by a flattened rib ; the inner 
volutions are inserted as far as the row of tubercles; ambit 
rounded ; aperture transversely elongated, and a little bian- 
gular, its width being twice its length ; septa but slightly 
concave, with their edges a little waved. 
Found in the Red Limestone at Closeburn, Dumfriesshire, 
by C. G. S. Menteith, Esq. 
31. N. dorsalis. — The Back-siphuncled Nautilus, pi. 
XXV. fig. 1. 
Nautilus dorsalis. Phillips, Geology of Yorkshire, II. p. 
231, pi. 17, fig. 1 7> and pi. 18, figs. 1 and 2. 
