228 MOLLUSCA. CErHALOPODA. Nautilus. 



Colour opake broivn. Chambers tliminishing in size to the mouth, which 

 is contracted. Syphon near the distal margin, produced. The partitions are 

 represented in Montagu's figure as tuberculated, though this character is 

 not noticed in the description. 



4. S. carinatula. — Outer margin sliglitly carinated. Cham- 

 bers increasing regularly in size. 



N. oblongus carinatus apertura lineari ovali, Walker, Test. Mm. t. iii. 

 f. Ti.—Mont. Teat. Brit. 195. 



Colour white, transparent. Chambers seven. The first globose. Montagu 

 states, that the drawing of this shell, sent to him by Mr Boys, differs from 

 the figure which Walker published, — an occurrence too frequent in the same 

 (juarter, 



Gkn. III. NAUTILUS.— Sides equal; the last whorl em- 

 bracing and concealing tlie previously formed ones. 



5. N. crlspus. — Exteriorly carinated. Spaces between the 

 partitions crenatcd. Sides convex. 



Linn. Syst. i. 11G2. Walker, Test. Slin. t. iii. 65. Mont. Test. BriU 



I87. t. xvlii. f. 5 Among old shells and corals — Common. 



Size about g'jjth of an inch. Chambers in the last whorl about 20; the par- 

 titions fiexuous, elevated, canaliculated. ]\Iouth cordate ; the aperture or 

 syphon minute, near the proximal edge. In the young shells, the partitions 

 are destitute of the gutter, and the mai'gin is more rounded. 



6. N. calcar. — Exteriorly carinated. Spaces between the 

 partitions smooth. Sides convex. 



Mont. Test. Brit. 189. t. xv. f. 4.— N. rotatus, Titrt. Conch. Diet. 118 — 

 On shells and corallines on the English coast. 

 Chambers in the last whorl 6 ; the partitions marked by elevated flexuouR 

 lines, which do not reach, however, to the carinated margin. ]\Iouth semi- 

 cordate, clasping. 



7. N. Icevigahdus. — Exteriorly subcarinated. Mouth Avith 

 a rim. Sides convex. 



N. spiralis geniculis Irevibus, Walker, Test. Min. 19. t. iii. f. 67- Mont. 

 Test. Brit. 188 ; Suppt. lb. t. xviii. f. 7-8 — English or Scottish shores. 

 Chambers about 10, glossy, smooth ; the partitions marked by subelevated 

 flexuous rays. Mouth triangular, with a rim which does not clasp the body 

 whorl. Aperture near the distal edge. The mouth seems liable to var_y in 

 form, as in a specimen which I found in Zetland, in which it is rounded and 

 turned to one side. 



8. N. deprcssulns. — Depressed, exteriorly rounded ; the cham- 

 bers and partitions nearly even. 



N. spiralis utrinque subumbilicatus geniculis depressis plurimis, Walker, 

 Test. Min. 19. t. iii. f (i8.~N. dep. Mont. Test. Brit. 190; Suppt. 78. 



t. xviii. f 9 English and Scottish shores. 



Chambers about nine in number ; the partitions slightly curved, ending at 

 the centre in a pellucid spot. 



9. N. uvihilicatulus. — Depressed, exteriorly rounded ; parti- 

 tions sunk, with a subtuberculated elevation in the middle. 



