CARINARIA. 195 



type of their organization agrees with that of the Gastero- 

 poda, it passes through a wide degree of modification. 



The ventral disc, for example, which presents a prominent 

 feature in the rest of the class, is here represented by a 

 gelatinous fin, by aid of which the mollusk, being scarcely 

 ever at rest, swims longitudinally on the water with his 

 shell downward. 



The solitary genus Carinaria was instituted by Lamarck 

 for the purpose of distinguishing a beautifully transparent 

 shell, commonly known as the Glassy Nautilus, which, as 

 already stated, is designed to cover a small nucleus con- 

 taining the organs of respiration. This trans])arent shell 

 may be compared, in its appropriation, to those elegant 

 glass shades beneath which exotic ferns are often nurtured. 



Carinarice are very abundant in the Mediterranean and 

 Indian seas ; they congregate in considerable numbers, but 

 are rarely visible except at night. 



Beautiful Carinaria, with thy glassy shell, surely thou 

 art one of the greatest wonders in the deep, though thyself 

 but small. Men tliink much of that strange substance 

 which opens to the naturalist a miniature world, and assists 

 the astronomer in discovering i\q\y stars, which excludes 

 the wind and rain, and enables the inhabitant of northern 



