ARGONAUTA-/MP# SAILOR. 139 



last volution takes a straight direction, and is re- 

 mote from the adjoining one : aperture orbicular, 

 pearly within ; chamber^ separated by pearly 

 plates, but communicating with each other by a 

 small siphunculus ; white or cream colour. 



This shell is so exceedingly brittle that perfect 

 specimens are very rare. The last chamber, which 

 is the one inhabited by the animal, is a straight 

 cylinder, but it is so fragile that it is very seldom 

 that any vestige of it is preserved. In the broken 

 state in which these shells are found, they resem- 

 ble a ram's horn, and so they have been descri- 

 bed, but when complete, they have more the ap- 

 pearance of the crosier. The mouth of the ani- 

 mal is surrounded by ten arms, two being longer 

 than the others. This Nautilus is found in great 

 numbers in the West Indies. 



Genus. ARGONA UTA.* Plural, Argonauts. 



PAPER SAILOR. 



Generic Character. Shell univalve, involuted, 

 the last whorl very large, having a double tuber- 

 culated carina, thin, transparent, unilocular ; aper- 

 ture cordate, entire, contracted. This shell has 

 much the appearance of being composed of two 



* Plate VI. figure 5. 



