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"— Ajrf. Conch. 1048. ? Smccr. Min. Conch, t. cxxiv. (transversely oval. — 

 Inferior Oolite, Norton-under-Ham. 



11. N. bilobaitis. —'■'■ Subglobose, umbilicated; septa two-lobed ; aperture 

 three or four times as wide as long." Margin a little flattened ; umbilicus 

 small, nearly cylindrical ; syphon central.— Soiver. Min. Conch, t. ccxUx. 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." — Sower. Min. Couch, t. ccclv. — In 

 London Clay. 



13. N. radiatus. — "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 suddenl)%" — Flem. AVern. 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 gi'oove ; 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. cxxv. — 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 strise elevated. — Sower. 

 Min. Conch, t. clxxxii — In Lias, Lyme Regis. 



18. "N.pentagonus. — "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. ccxlix. 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." Sower. Min. Conch, t. ccxlix. f 4 — In the limestone of the Old 



Red Sandstone, Closeburn. 



20. N. Luidii. Whorls apparent, rounded with longitudinal serrated strife ; 



septa concave, with the syphon placed near the exterior margin — INIartin, 

 Petrificata Derbiensia, t. xxxv. Il 12. — In clay in the Coal formation, Derby- 

 shire. 



21. N. ira^e«s.— Volutions three, nearly external, even, round, gradually 

 tapering ; septa oblique, slightly waved — Mart. Pet. Derb. t. xli. £ 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 



