230 MOLLUSCA. CEPHALOPODA. Nautilus. 
10. N. ohesus — “ Gibbose, umbilicate, plain; back broad, flat; mouth 
large, squarish ; septa very numerous, not recurved ; siphuncle nearly cen- 
tral.” — List. Conch. 1048. ? Sower. Min. Conch, t. exxiv. (transversely oval 
Inferior Oolite, Norton-under-Ham. 
11. N. hilobatus.—'-^ Subglobose, umbilicated; septa two-lobed ; aperture 
three or four times as wide as long.” Margin a little flattened ; umbilicus 
small, nearly cylindrical ; syphon central. — Sower. Min. Conch, t. eexlix. f. 2, 
3. — In the Limestone of the Old Red Sandstone, Closeburn, Dumfriesshire. 
12. N. regalis — “ Gibbose, plain, not umbilicate; front flattish; sides con- 
vex ; aperture rather wider than long.” — Smver. Min. Conch. U ccclv. — In 
London Clay, 
13. N. radialus. — “ Gibbose, umbilicated; surface marked with curved ra- 
diating undulations ; sides and front rounded ; aperture orbicular, deeply in- 
dented.” — Sower. Min. Conch, t. ccclvi. — In Green Sand, Maltor. 
14. N. Wrightii. — “ Gibbose, smooth, rounded exteriorly, partitions distant, 
slightly waved ; syphon nearer the exterior than the centre of the chamber ; 
shell increasing rather suddenly.” — Flem. Wern. Mem. iii. 96. I owe the 
specimen of this species which I possess to Samuel Wright, Esq., who found 
it in the Transition Limestone, Cork. It bears a near resemblance in form to 
N. elegans. 
In the twelve following species, the inner whorls are more or less conspi- 
cuous, in consequence of the body-whorl not clasping the inner whorls so 
completely as in the preceding species. 
15. N. discus — “ Depressed, edge flat, aperture oblong, volutions not con- 
cealed by each other.” Outer edge of the aperture narrower than the inner 
one, and notched by a marginal groove ; syphon near the inner edge.— Sower. 
Min. Conch, t. xiii. — In Carboniferous Limestone, Kendal. 
16. N. intermedins.^^'' Gibbose, umbilicate, concentrically striated; back 
broad, flattened, mouth squarish : siphuncle nearest the external edge.” — 
Sower. Min. Conch, t. exxv. — In limestone in the Lias at Keynsham. 
17. N. striatus. — “ Slightly depressed; umbilicate; concentrically stri- 
ated ; aperture half the diameter of the shell, nearly orbicular.” — The whorls 
increase rapidly ; the front a little compressed ; the striae elevated. — Sower. 
Min. Conch, t. clxxxii — In Lias, Lyme Kegis. 
18. 'pentagmius ‘‘Discoid, subcarinated ; inner turns partly concealed; 
aperture orbicular, obscurely 5-angled, and impressed by the preceding whorl, 
nearly half the diameter of the shell.” Sides a little flattened ; septa not 
very concave, with a central siphuncle.” — Sower. Min. Conch, t. eexlix. f. 1. 
—In limestone of the Old Red Sandstone, Closeburn. 
19. N. tuberculatus “ Discoid, thick, largely umbilicate; one row of large 
tubercles on each side ; front rounded ; aperture transversely elongated, 2- 
angled.” — Smjoer. Min. Conch, t. eexlix. f. 4 — In the limestone of the Old 
Red Sandstone, Closeburn. 
20. N. Luidii. — Whorls apparent, rounded with longitudinal serrated striae ; 
septa concave, with the syphon placed near the exterior margin — Martin, 
Petrificata Derbiensia, t. xxxv. £ 12 — In clay in the Coal formation, Derby- 
shire. 
21. N. ingens. — Volutions three, nearly external, even, round, gradually 
tapering ; septa oblique, slightly waved — Mart. Pet. Derb. t. xli. f. 5 — In 
Carboniferous Limestone, Derbyshire. This is probably the species which Ure 
refers to in his Natural History of Rutherglen and Kilbride, p. 307- “ The 
