ARGONAUTA PAPER SAILOR. 139 



line ; the last volution takes a straight direction, 

 and is remote from the adjoining one : aperture 

 orbicular, pearly within ; chambers separated 

 by their pearly plates, but communicating with 

 each other by a small siphunculus ; white or 

 cream colour. 



This shell is so exceedingly brittle that per- 

 fect specimens are very rare. The last chamber, 

 which the animal inhabits, is a straight cylinder, 

 but it is so fragile that it is very seldom 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 

 appearance of the crosier. The mouth of the 

 animal is surrounded by ten arms, two being 

 longer than the others. This Nautilus is found 

 in great numbers in the West Indies. 



Genus. ARGON AUTA.f (Plural, Argonautce.) 



PAPER SAILOR. 



Generic Character. Shell univalve, involuted, 

 the last whorl very large, having a double tuber- 

 culated carina, thin, transparent, unilocular ; 

 aperture cordate, entire, contracted. This shell 



* Plate VI. figure 5. 



