ARGON AUTA. 29 



CHAPTER V. 



Third Division. — Univalves, 



" Father," said Lucy, the next time they met 

 to pursue their study, " I think we have made 

 ourselves famihar with the various hinges of the 

 bivalve shells, which are becoming favourites with 

 us ; but from the variety of fine specimens which 

 you have on your table, I see that we shall 

 be much gratified in examining the univalve 

 division." 



" My first genus is very beautiful," replied 

 Mr. Elliot ; "it is Argonauta, or paper-sailor. 

 The shell is univalve, involute, unilocular, or 

 without chambers : the aperture cordate. (Plate 

 6.) These shells are spiral, and remarkably 

 brittle. The argonauts are supposed to be the 

 shells that taught mankind the use of sails in the 

 earliest ages of society. In calm weather the 

 animal rises with its shell to the surface of the 

 water, and spreads its arms over the edge ; these 

 arms answer the purpose of oars. It then spreads 

 a membrane for a sail, which can be turned in 

 any direction, and is impelled forwards by the 



