CATECHISM OF CONCHOLOGY. 49 



expert management of this instinctive sailor ; thus 

 noticed by Pope in the following lines : 

 " Learn of the little Nautilus to sail, 



Spread the thin oar, and catch the driving gale." 



This curious shell-fish swims on the surface of 

 the sea; the shells serve for a boat, a membrane 

 which it extends at pleasure, for a sail, and two 

 feet, or tentacula, as oars. On the approach of 

 danger, this active little mariner suddenly hauls 

 in his tackle, rapidly absorbs a quantity of sea 

 water, and betakes himself to the fathomless 

 abyss, his native dwelling. 



CHAP. XXII. 



UNIVALVES. 

 NAUTILUS ; Pearly Sailor. 



Q. IN what respect does the Nautilus differ 

 from the Argonauta ? 



A. The shell of the former is many -chambered, 

 while that of the latter is without any. The 

 divisions are perforated and connected by a con- 

 tinued syphon, or pipe, formed of a thin testa- 

 ceous matter, and lined with a membrane of the 

 animal. 



