V 
Nautilus. MOLLUSCA. 33 
umbilicus; ambit very broad, with its centre plain, flat, and 
provided with twocarinse on each side, and a rounded broader 
one outside of these, with a considerable smooth space inter¬ 
vening betwixt them and the edge of the umbilicus ; lip pro¬ 
vided with a deep sinus. 
This species has some affinity to Nautilus multicarinatus, 
but it is provided with a narrow concave space in place of 
the keel upon each side; 
In its general contour it somewhat resembles also Nautilus 
biangulatus pi. 23, fig. 9; but in addition to the angles which 
distinguish that shell, it is provided on each side of its broad 
and flattened front with two minor keels. 
Found in the Black-Rock, Cork, Ireland. 
6 . N. cyclostomus. — The Circle Nautilus, pi. XXII. 
fig. 20 . 
Nautilus cyclostomus. Phillips, Geology of Yorkshire, II. 
p. 232, pi. 22, fig. 26, pi. 17, fig. 29, and pi. 18, fig. 3. 
Shell partly spiral ; inner volutions exposed, and the outer 
ones rapidly increasing in size, to a nearly straight line ; 
sides crossed by fine flexous stria? ; sutures outwardly con¬ 
cave, and slightly retroflected on the back ; aperture almost 
circular; siphunculus placed near the outer edge; number of 
volutions variable. 
Found at Castleton and Bolland, Queen’s County, Ireland; 
and also at High-Green-Wood. 
7. N. pentagonus. —The Pentagonal Nautilus, pi. xxii. 
%. 21 . 
Nautilus pentagonns. Sowerby, Min. Conch. III. p. 89, 
pi. 249, fig. 1. Fleming, Brit. An. p. 230. 
Discoidal, with five volutions ; the inner ones concealed 
to the extent of one-third, and increasing rapidly in size ; 
ambit subcarinated; aperture orbicular, obscurely five angled, 
and considerably indented by the preceding volution, and 
extending to nearly half the diameter of the shell ; sides 
somewhat flattened, with a few oblique, slight wrinkles; 
septa rather numerous, and slightly concave ; the siphuncle 
central. Greatest diameter eight and a-half inches. 
In the young condition, the aperture is less pentangular 
than in the adult. 
Discovered in the Black Limestone at Bathgate, Linlith¬ 
gowshire, and has since been found in the Red Limestone, at 
Closeburn, Dumfriesshire. 
8 . N. sinuatus. — The Sinuous Nautilus, pi. XXII. 
fig. 22 . 
Nautilus sinuatus. Sowerby, Min. Conch. II. p. 213, pi. 
194. Fleming, Brit. An. p. 231. De la Beche, Geo. 
Manual, p. 369* 
Very thick, umbilicate ; inner volutions few, and entirely 
concealed ; sides depressed, conical, with close, moderately 
fine, and elevated concentric stria?, which gradually become 
obsolete towards the aperture ; ambit convex; aperture 
obtusely sagittate and truncated ; septum greatly elevated 
towards the front, with a large marginal sinus on each side; 
umbilicus very shallow ; siphunculus placed a third the 
length of the aperture from the ambit. Greatest diameter 
five inches; and its thickness two and a-half inches. 
Found in the Inferior Oolite at Yeovil. 
9 . N. asta co ides. — The Little Lobster Nautilius, pi. 
XXIII. fig. 1. 
Nautilus astacoidcs. Phillips, Geology of Yorkshire, I. 
p. 163, pi. 12, fig. 16. De la Beche, Geo. Manuel, p. 369- 
Shell discoidal subumbilicate; inner volutions entirely 
concealed ; ambit narrow towards the inner side next the 
aperture, but greatly thickened as it approaches the aperture 
behind ; sides smooth, concentrically lineated, with transverse 
lines of growth ; aperture very expansive, occupying nearly 
two-thirds the diameter of the shell, and rounded towards 
the back ; siphuncle nearly central. 
bound in the Upper Shale of the Lias formation of York¬ 
shire. 
10. N. undulatus. — The Waved Nautilus, pi. XXIII. 
fig. 2. 
Nautilus undulatus. Sowerby, Min. Conch. I. p. 87, pi. 
40. Homing, Brit. An. p.229. De la Beche, Geo. Manuel, 
p. 293. 
Gibbous ; inner volutions concealed ; sides considerably 
produced, with large undulations, which arc more deeply 
defined as they approach towards the back, and reaching to 
more than half the diameter; edge of the back, when viewed 
in profile, deeply scalloped ; aperture somewhat obcordate; 
siphuncle nearly central ; septa rather numerous, each crossed 
on the surface by an undulation ; thickness half the diameter 
of the disk. Greatest diameter twelve inches. 
Found in the Greensand at Nutficld, Surrey. 
11. N. oxystomus. — The Sharp-Mouthed Nautilus, pi. 
XXIII. fig. 3. 
Nautilus oxystomus. Phillips, Geology of Yorkshire, II. 
p. 233, pi. 22, fig. 35, 36. 
Lenticular, greatly depressed ; consisting of four volu¬ 
tions, the inner ones half exposed; sides smooth ; ambit 
acute ; septa outwardly concave, as exhibited in the figure. 
Found in Limestone, at Enniskillen and Florence Court, 
Ireland, and in the Isle of Man. 
12. N. truncatus. —The Truncated Nautilus, pi. XXIII. 
fig. 4. 
Nautilus truncatus . Sowerby, Min. Conch. II. p. 49? pi. 
123. Fleming, Brit. An. p. 229 . De la Beche, Geo. 
Manuel, p. 369. Lister’s Conchology, No. 1048. 
Thick, inner volutions entirely concealed, umbilicate; 
sides flattened ; ambit flat; aperture elongated and quad¬ 
rangular, extending to nearly half the diameter of the disk, 
narrowest towards the ambit; siphuncle oval, placed nearest 
the inner end of the aperture, or inner margin of the septum ; 
septa very numerous, but not recurved towards the umbilical 
region ; thickness not quite half the diameter. 
13. N. simplex. —The Simple Nautilus, pi. XXIII. fig. 5. 
Nautilus simplex. Sowerby* Min. Conch. II. p. 47, pi. 
122. Fleming, Brit. An. p. 229. De la Beche, Geo. 
Manuel, p. 293. 
Spheroidal depressed ; inner volutions entirely concealed ; 
sides plain, umbilicate; aperture lunate, with truncated 
angles, which embrace the sides of the volutions; septa 
numerous and somewhat flattened ; siphuncle situated near 
the inner edge of the septum ; thickness nearly four-fifths, 
the greatest diameter of the disk, which varies from an inch 
to thirteen inches. 
Found plentifully in the Greensand, near Boreham, in 
the vicinity of Warminster. 
This shell bears a considerable similitude to N. imperial is, 
pi. 24, fig. 5, but is more rounded in its curvature, and 
somewhat narrower and flatter in the middle. 
14. N. excavates. — The Excavated Nautilus, pi. XXIII. 
fig. 6. 
Nautilus cxcavatus. Sowerby, Min. Conch. VI. p. 55, pi. 
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