228 MOLLUSC A. CEPHALOPODA. Nautilus, 



Colour opake brown. Chambers diminishing 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 slightly carinated. Cham- 

 bers increasing regularly in size. 



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

 f. 72.— Mont. Test. 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 

 quarter. 



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

 bracing and concealing the previously formed ones. 



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

 partitions crenated. Sides convex. 



Linn. Syst. i. 11 62. Walker, Test. Min. t- iii. 65. Mont. Test. Brit. 



187- t. xviii. £ 5 Among old shells and corals — Common. 



Size about i.^th of an inch. Chambers in the last whorl about 20; the par- 

 titions flexuous, elevated, canaliculated. Mouth cordate; the aperture or 

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

 are destitute of the gutter, and the margin 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, Turt. Conch. Diet. 118 — 

 On shells and corallines on the English coast. 



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

 lines, which do not reach, however, to the carinated margin. Mouth semi- 

 cordate, clasping. 



7. N. Icevigatulus. — Exteriorly subcarinated. Mouth with 

 a rim. Sides convex. 



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

 Test. Brit. 188; Suppt. 75. 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 vary in 

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

 turned to one side. 



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

 bers and partitions nearly even. 



N. spiralis utrinque subumbilicatus geniculis depressis plurimis, Walker, 

 Test. Min. 19. t. iii. f. 68.— 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. iimbU'icatidus. — Depressed, exteriorly rounded ; parti- 

 tions sunk, with a subtuberculated elevation in the middle. 



