DESCRIPTION. 
137 
Specimen white, with undulated, smooth, and 
bifurcated ribs ; teeth of the keel brown towards 
the apex, extremely thin and brittle. 
Inhabits the Mediterranean and Indian Ocean. 
Fig*. 2. Nautilus Pompilius. 
Shell with a cordate aperture, whorls obtuse and 
smooth. 
Lister Conch. Tab. 550. Fig. 1, 3. 
Specimen white, with flexuous yellowish tawny 
rays and streaks : the inner whorls dark brown ; 
interior surface fine mother-of-pearl ; umbilicus 
pervious. 
Inhabits the Indian and African Ocean. 
Fig. 3. N. Spirilla. 
Shell with an orbicular aperture ; whorls cylin- 
drical, remote. 
Lister Conch. Tab. 550. Fig. 2. 
Specimen white, within pearly ; whorls gradu- 
ally decreasing towards the point of the spire ; the 
last whorl excentric, continued, in a perfect shell, 
into a long cylindrical straight tube ; siphun cuius 
lateral. 
Inhabits the American and Indian Ocean, 
