21 
SHELL GALLERY. 
Case 96. 
Case 97. 
Case 97. 
mata) are provided with small glassy shells ; others (G-ymnosomata) 
are naked. They exist in countless millions in some parts of the 
Fig. 17. 
b 
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 
Fisr. 18. 
Sea-Hare (Tethys (Aplasia) punctata). British. 
a, labial tentacles ; 6, 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 Umbraculum 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 Nudibranchs or Naked-gilled Molluscs comprise some of the 
