MOLLUSCA OR UNIVALVES. 219 



latter entire. The Zoophaga are all marine, 

 and all appear to have two tentacula ; they are 

 predaceous, as their name implies, and feed for 

 the most part on other shell-fish, either living 

 or in a decayed state. 



Family 11. — Canaliferidce* 



The animals of this family breathe water 

 only; they feed on animal substances by the 

 help of their retractile trunk, and are confined 

 entirely to the sea. The shells are spiral, en- 

 closing the animal, the aperture having a canal 

 either long or short. All have opercula. The 

 family is divided into two parts : in the first the 

 periodical growth of the shell is but slightly 

 marked; in the second it is distinguished by 

 thickened bands or varices, which remain on 

 the external whorls. Seven genera belong to 

 the first division, and four to the last. 



DIVISION I. 



* 85. Cerithium. — Shell turreted, and much 

 elongated ; mouth oblong and oblique, having 



* Les Canaliferes, Lamarck. 



