Nautilus. 
MOLLUSCA. CEPHALOPODA. 
N. spiralis umbilicatus geniculis sulcatis, Walker^ Test. Min. 19. t. iii. 
f. 69 — N. umb. Mont. Test. Brit. 191 ; Suppt. 78. t. xviii. f. 1 — Eng- 
lish and Scottish shores. 
Chambers ten, rounded on the sides, but nearly even on the margin, with 
a frosted appearance on the surface. Partitions flexuous, ending at the centre 
in a pellucid spot. The geographical range of this species is extensive. It 
occurs on the coasts of Devon and of Zetland, and I have even detected it on 
corallines found on the surface of the sea, about the middle of Hudson’s 
Straits, in 1821, by Captain Parry. 
10. N. Depressed, iimbilicated, and shewing part 
of the interior volution. 
N. spiralis, crassus, utrinque umbilicatus, geniculis lineatis, Test. 
Min. t. iii. f. 70. — N. crassulus, Mont. Test. Brit. Suppt. 79. t. xviii. 
f. 2. — English coast, rare. 
Shell opake brown, with numerous close-set elevated joints. Sides similar. 
Mouth placed a little oblique, scarcely clasping the body, and furnished with 
a syphon — The internal structure of these recent species can scarcely be sa- 
tisfactorily determined. 
EXTINCT SPECIES. 
1. N. imperialis .‘ — “ Involute, umbilicate. Aperture lunate. Septa entire, 
concave, broadest in the middle, truncated, and slightly recurved at their 
ends. Siphunculus nearest to the inside.” — Sowerhy's Mineral Conchology, 
t. i. — In the London clay, Highgate. 
2. N. centralis — “ Involute umbilicate. Aperture bluntly lunate. Sej)ta 
entire, concave, not recurved at their ends. Siphunculus central.” — Sowerhy's 
Min. Conch, t. i. left hand figure — London day. 
3. N. incequaUs.~.-~‘-‘' Spheroidal umbilicate, aperture nearly round ; septa 
distant in the inner whorls, and approaching near together in the outer 
whorls ; siphunculus near the inner margin of the septum.” — Sower. Min. 
Conch, t. xl. lower figures. — In Chalk Marl., Folkstone. 
4. N. undulatus.—J-^ Gibbose; surface largely undulated, sides rather coni, 
cal, edge flat; aperture obcordate, inner whorls concealed.” Siphunculus 
near the centre. — Sower. Min. Conch, t. xl. In Green Sand., Nutfield, Surrey. 
5. N. Uneatus . — “ Flatted spheroidal, umbilicate, surface obscurely striated, 
back flat, broad, with a concave line in the interior (which appears convex 
around the cast). Aperture rather square, deeply indented b}^ the preceding 
whorl, septa numerous, concave, siphunculus central.” — Sower. Alin. Concln 
t. xli . — Inferior Oolite^ Comb-down, Bath. 
6. N. elegans — “ Gibbose, umbilicate, with numerous linear, reflexed, ra- 
diating sulci.” — Siphunculus central. — Soiver. Min. Conch, t. exvi. Mantell's 
Fossils of the South Downs, p. 112, t. xx. f. 1. — In Chalk Marl, Sussex. 
7* N. Cmnptoni — “Lenticular, carinated; centre covered; surface smooth; 
keel obtuse ; aperture acutely triangular.” Less than a line. — Sower. Alin. 
Conch, t. exxi — In Chalk Marl, Wilts. 
8. Iii . simplex . — “ Depressed, spheroidal, umbilicate, plain ; mouth lunate, 
with the angles truncate, embracing the preceding whorl ; siphuncle nearest 
to the inner edge of the septum.” — Sower. Min. Conch, t. exxii. In Green 
Sand. 
9. N. truncatus.—^^- Thick, flatted, plain, umbilicate; back flat, moutli 
elongated, four-angled ; siphuncle (oval) nearest to the inner margin of the 
fieptum.”— A'owcr, Min. Conch, t. cxxiii.— In Lias Limestone, Bristol. 
