NAUTILUS. 117 



NAUTILUS. 



Shell with a single valve, consisting of compart- 

 ments or cells, communicating with each other by 

 means of a small perforation or tube. 



A. With the spires detached. 1. 



B. With the spires connected. 2 to 12. 



C. Elongated, and more or less straight. 13 to 24. 

 L Nautilus Spirilla. Crosier Nautilus. Fig. 77- 



Lister, pi. 550. f. 2. 



Shell spiral, extremely thin and brittle, transparent, 

 white or cream-color: spires five, cylindrical, detached 

 from each other, divided into numerous chambers at nearly 

 equal distances, which are distinguished by a depressed 

 circular line on the outside ; the primary volution running 

 nearly straight and very remote from the next ; the re- 

 maining ones growing gradually less and closely involuted 

 but not touching each other ; the line of junction also be- 

 comes gradually deeper towards the smaller end, giving the 

 different divisions a more rounded appearance, till the ter- 

 minal ones appear somewhat globular : aperture orbicular, 

 perlaceous within, the chambers separated by thin pearly 

 plates, with a small tube of communication which is placed 

 near one side : diameter nearly an inch j of the larger volu- 

 tion nearly a quarter of an inch. 



Two specimens of this interesting addition to our native 

 stock, were .ound on the strand between Kenmare harbour 

 and Ballyskelligs bay, in the county of Kerry, Ireland, by 

 our intelligent and much respected friend, Mr. O Kelly of 

 Dublin, in the summer of 1817 ; where, as he observes, the 

 waves of the Atlantic come unbroken from the shores of 

 America j and where he also found at the same time, the 

 Helix ianthina with the amnial in it, and the rare Lepas 

 sukata. v. w. 



B. With the spires connected. 2 to 13. 



2. Nautilus lacustris. Fresh-water Nautilus. 



Montagu, pi. 6. f. 3 Walker, f. 28. 



Shell horn-eolor or rufous-brown, smooth, glossy, trans- 

 parent^ 



