140 UNIVALVES. 



pieces united by the keel, and seems to be the 

 link between the univalve and bivalve shells. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The animal inhabiting these elegant shells is 

 soft and fleshy, and has a large portion of its 

 body enveloped in the mantle ; its head is fur- 

 nished with two eyes, and round its mouth are 

 arranged like rays eight elongated and pointed 

 tentacula or arms. Two of these have a thin mem- 

 brane extending more than half their length. 

 This singular appendage the animal can expand 

 or draw in at pleasure. The shell is of a thin 

 paperlike substance, resembling in form a kind of 

 boat. Few objects can be conceived more inter- 

 esting than this beautiful animal seated in its 

 pearly little vessel : two tentacula erected with 

 their membrane unfurled like a sail, whilst the 

 remaining six, suspended over the sides of the 

 little bark, perform the office of oars. When 

 wafted by propitious gales, it calmly rides over 

 the waves : but should a storm threaten, or an 

 enemy approach, it precipitately hauls in its 

 tackle, shrinks into its shell, and drawing in 

 water to add to its weight, seeks protection in the 

 depths of the sea : the danger over, it diminishes 

 the gravity of its shell by ejecting the water, and 

 rises again to the surface. 



