DICTIONARY OF TERMS. 



Adherent. - ■ 

 Adherent. - - 



Adherent. - - 

 Anterior. - 



Aperture. - • 



Apex. 



Articulation. 



Articulation. 

 Articulation. 



AUR1CULATED. 



Axis. - - 



Base. 



Base. 

 Beak. 



The Mollusca adhere to thin shells. 



A shell which attaches itself is adherent. Oysters 



adhere to rocks. 



An operculum is adherent, when fixed to the animal. 

 That half in Bivalve shells, which shows the 



cardinal ligament. 

 The mouth of a shell. 

 The tip, or small end of a shell. 

 The insertion of parts of shells into each other. 



The fossil Cornu Amnonis is an instance of a 



series of articulations. 

 The tentacula of the animals of Barnacles, have 



articulations. 



The teeth of bivalve shells are frequently articu- 

 lated within each other. 

 Having ears. The Pectens are auriculated. 

 In univalve shells the centre, or pillar, upon which 



the spires turn. 



B. 



The lower part of a shell, or that which is op- 

 posed to the summit, or point of the spire. 



The species of the genus Lepas, fix themselves by 

 their base, to rocks and other bodies. 



The elongated base, of certain species of univalve 

 shells, is called the beak. The genera Murex 

 and Sirombus, afford examples of beaked shells. 



