36 
MOLLUSCA. 
Nautilus. 
Discoidal, umbilicate; inner volutions entirely concealed, 
and rapidly increasing; sides rounded, smooth ; aperture 
sub-rotund; siphuncle placed close to the back; septa dis¬ 
tinct; umbilicus large and deep. 
Professor Phillips says, there are three varieties of this 
species : A, has a circular umbilicus, with the inner volutions 
partly concealed; B, umbilicus somewhat angular, with the 
volutions more involute ; C, umbilicus open and rounded, 
and the shell somewhat less involute. The two former are 
found at Bolland, Queen’s County, and the latter are from 
Kildare, Ireland. 
32. N. bistiualis. — The Doubly Striate Nautilus, PI. 
XXV. fig. 2. 
Nautilus bistrialis. Phillips, Geology of Yorkshire, II. p. 
232, pi. 17, % 2. 
Discoidal, umbilicate; inner volutions entirely concealed ; 
sides slightly rounded; umbilicus very large, but not deep, 
with several spiral stria? on its margin. 
Found at Bolland, Queen’s County, Ireland. 
33. N. goniolobatus.— The Corner-Lobed Nautilus, pi. 
xxv. fig. a 
Nautilus goniolobus. Phillips, Geology of Yorkshire, II. 
p. 232, pi. 17, fig. 23. 
Involute, subglobose, umbilicate; inner volutions wholly 
concealed ; sides smooth, inflated ; ambit rounded ; umbilicus 
small; sutures retroflexed in a small dorsal sinus ; first lateral 
lobe angular; the second cannot be traced 
Found at Bolland, Queen’s County, Ireland. 
34. N. ingens. —The Huge Nautilus, pi. XXV. fig. 4. 
Nautilus ingens, Phillips, Geology of Yorkshire, II. p. 232, 
pi. 18, fig. 4. De la Beche, Geo. Manuel, p. 428. 
Discoidal; inner volutions slightly concealed, and increasing 
rapidly; sides smooth; ambit round; aperture orbicular, 
obscurely angular towards the inner edges; siphuncle round, 
placed at about a third the length of the aperture from the 
ambit; septa numerous. It is a very large species. 
Found at Coniston, near Gargrave; and at Clattcring- 
dykes, in the Mountain Limestone. 
It is nearly allied to N . pentagonus , pi. 22, fig. 21, but may 
be distinguished from it by the rounded ambit. 
35. N. lineatus —The Lineated Nautilus, pi. XXV. fig. 7. 
Nautilus Uncatus. Sowerby, Min. Conch. I. p. 89, pi. 41. 
Fleming, Brit. An. p. 229. De la Beche, Geo. Manuel, 
p. 369- 
Spheroidal, compressed, umbilicate; inner volutions entirely 
concealed; sides slightly flattened, and obscurely striated 
transversely ; umbilicus small and well defined; ambit flat, 
broad, with a spiral concave groove in its centre; aperture 
somewhat quadrangular, with a deep indentation from the 
preceding volution; siphuncle placed near the middle; septa 
very numerous and concave, with three slight marginal 
undulations; diameter about a third longer than its thickness. 
Found in the Inferior Oolite at Combdown, near Bath. 
36. N. sulcatulus. — The Sulcated Nautilus, pi. XXV. 
fig. 8. 
Nautilus sulcatulus, Phillips, Geology of Yorkshire, II. 
p. 233, pi. 17, figs. 18 and 25. 
Discoidal; inner volutions quadrangular, partly exposed; 
sides smooth, concave towards the outer edge, and convex 
towards the marginal slope, which terminates abruptly, with 
many acute sigmoidal, transverse, and a few spiral striae ; 
volutions quadrangular; ambit concave along its centre, and 
somewhat bevelled to the sides; aperture oblong, some¬ 
what ten-sided ; siphuncle situate near the outer edge. 
Found at Iligh-Green-Wood, and Kildare, Bolland, and 
Coalbrookdale. 
37. N. elegans. —The Elegant Nautilus, pi. XXV. fig. 10. 
Nautilus elegans. Sowerby, Min. Conch. II. p. 33, pi. 116. 
Fleming, Brit. An. p. 229* Mantel!, Geology of Sussex, 
p. 112 and 197, pi. 20, fig. 1. pi. 21, figs. 1, 4, 8. De la 
Beche, Geo. Manuel, p. 293. 
Subglobose, umbilicate; inner volutions one-third con¬ 
cealed ; sides with numerous transverse, linear, curved, 
reflexed sulci, which divide the surface into broad flat ribs, 
which, after forming an elegant curve on the ambit, proceed 
laterally, and are then reflected towards the umbilicus; aper¬ 
ture obtusely sagittate; the siphuncle large, placed central; 
septa concavo-convex, entire, undulating in a gentle man¬ 
ner, with their convex surface placed in an opposite direction 
to that of the grooves, and decussating them ; umbilicus very 
small. Greatest diameter twelve inches; its greatest thickness 
is equal to about twice its width. 
This species is pretty widely diffused, and is met with in 
the Gray Chalk Marie of Stoneham, Hamsey, Otfham, Kans- 
combe, Middleham, and Firle, in Sussex. 
In a young condition, the furrows are wide, and separated 
by sharp transverse ribs, and the whole surface is ornamented 
with numerous well defined stria?. 
38. N. annularis. — The Hinged Nautilus, pi. XXV. 
fig. 11. 
Nautilus annularis. Phillips, Geology of Yorkshire, I. 
pi. 12, fig. 18. 
Discoidal, with a large circular annulation; sides gently 
raised; aperture very large; septa remote, and but slightly 
curved. 
Found in the upper Lias Shale of Yorkshire. 
39. N. rega us.—The Koyal Nautilus, pi. XXV. fig. 12. 
Nautilus regalis. Sowerby, Min. Conch. IV. p. 77, pi. 355. 
Fleming, Brit. An. p. 230. 
Gibbosc, destitute of an umbilicus; inner volutions entirely 
concealed ; sides plain and convex; ambit flattened; aper¬ 
ture somewhat wider than long; sides expanded, with a 
considerable indentation by the volution, and a little straight 
next the back. Largest diameter about nine inches, and its 
thickness about five. 
This species somewhat resembles N. imperialism pi. 24, 
fig. 5, but differs in its volutions, increasing more rapidly 
than in that shell, and its solid axis. In the young state, it 
may also be distinguished by the convex sides of the aperture. 
Found in the London Clay, at a depth of sixty feet, 
Regent’s Canal, Hyde Park, and Island of Sheppey. 
40. N. expan sus. — The Expanded Nautilus, pi. XXV. 
figs. 13 and 14. 
Nautilus expan sus. Sowerby, Min. Conch. V.p. 83, pi. 458. 
fig. 1. De la Beche, Geo. Manuel, p. 293. 
Subglobose, umbilicate; inner volutions wholly concealed ; 
sides with fine, sharp, transverse stria?, which following the 
lines of growth, pass from the umbilicus in an elegant sweep 
over the rounded back, and proceed continuously to the 
umbilicus on the opposite side ; umbilicus small, and nearly 
circular; aperture transverse, very greatly exposed, laterally, 
so much so as to make the axis considerably longer than the 
diameter of the shell ; the septa intersect the stria?, and in 
front their edges are nearly straight. 
