146 A Guide to the Zoological Collections. 



by the rapid opening and closing of the valves of the shell 

 in a flying fashion. The young of Spondylus can also move 

 in the same manner. The Oysters are always, except in 

 their very earliest stageSj permanently fixed. 

 The Ostracea are represented in every part of the globe. 



The student of Malacology should consult the article 

 Mollusca by Professor Ray Lankester in the latest edition 

 (1883) of the Encyclopedia Britannica. 



