24 



SHELL GALLERY. 



Case 96. 



Case 97. 



Case 97. 



mata) are provided with small glassy shells ; others (G-ymnosomata) i 

 are naked. They exist in countless millions in some parts of the ; 



Fig. 17. 



Shell-less Pteropod (Clione limacina). 

 a. Dorsal view. b. Ventral aspect. 



ocean, discolouring the water for miles. They constitute the princi- 

 pal food of the Baleen Whales. 



About a hundred species are known. 



The Sea-Hares, so called on account of a slight resemblance to a 

 crouching hare and not for their nimbleness of foot, are found in 



Fiff. 18. 



Sea-Hare (Tetliys (^Aplysia) punctata). British. 



a labial tentacles; h, upper tentacles or rhinophores; c, siphonal fold 

 of the mantle near the shell ; d, eye. 



most parts of the world, in pools at low water. At the hinder part 

 of the back two flaps of the mantle partly conceal a thin horny shell 

 which serves as a protection to the gills and vital organs beneath. 

 "When molested, these animals discharge a large quantity of a purple 

 fluid, discolouring the surrounding water for a distance of more than 

 a yard. 



The shell of Umbracidum is shaped very like that useful article, 

 an umbrella, of the Chinese pattern. The animal is very large, 

 having its breathing-organs on the right side below the shell. 



The Nudihramhs or Naked-gilled Molluscs comprise some of the 



