NAUTILUS. ARGONAUTA. 



145 



with transverse rufous flames gradually ceasing 

 towards the lip; diam. 7f- W. Nautilus. 13. 1. 

 N. UMBiLiCATULus. Sub-orbicular, umbili- 

 cated on both sides; all the whorls manifested 

 within the umbilicus ; sides of the whorls obtusely 

 wrinkled; aperture rounded, heart-shaped ; colour 

 much resembling the preceding. 6. 



ARGONAUTA. 



Shell univalvey unilocular, involute, very thin; spire 

 bicarinate, tuberculous, re-entering the aper- 

 ture. 



A. ARGO. Large, involute, very thin, white, 

 sides transversely ribbed ; ribs frequent, forked 

 near the keel; carinae approximate, tubercular, 

 partly blackish red ; tubercles small, very nu- 

 merous. S. 485. 



H 



