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. crassulus. — Depressed, umbilicated, and shewing part 

 of the interior volution. 



N. spiralis, crassus, utrinque umbilicatus, geniculis lineatis, Walker, 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." — Sowerbtfs Mineral Conchology, 

 t. i. — In the London clay, Highgate. 



2. N. centralis " Involute umbilicate. Aperture bluntly lunate. Septa 



entire, concave, not recurved at their ends. Siphunculus central." — Sowerby's 

 Min. Conch, t. i. left hand figure — London clay. 



3. N. incequalis. — " 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 " 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. lineatus. — " 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 by the preceding 

 whorl, septa numerous, concave, siphunculus central." — Soiver. Min. Conch, 

 t. xli Inferior Oolite, Comb-down, Bath. 



6. N. elegans " Gibbose, umbilicate, with numerous linear, reflexed, ra- 

 diating sulci."— Siphunculus central. — Sower. Min. Conch, t. cxvi. Mantell's 

 Fossils of the South Downs, p. 112, t. xx. f. 1 — In Chalk Marl, Sussex. 



7- N. Comptoni " Lenticular, carinated ; centre covered ; surface smooth ; 



keel obtuse ; aperture acutely triangular." Less than a line. — Sower. Min. 

 Conch, t. cxxi In Chalk Marl, Wilts. 



8. N. 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. cxxii. In Green 

 Sand. 



9. N. truncatus.— u Thick, flatted, plain, umbilicate; back flat, mouth 

 elongated, four-angled ; siphuncle (oval) nearest to the inner margin of the 

 septum." — Sower. Min. Conch, t. exxiii.— In Lias Limestone, Bristol. 



