MOLLUSCA OR UNIVALVES. 



187 



54. Melanopsis. — Shell turreted ; mouth 

 nearly entire, having a slight notch A 



having from five to fifteen whorls ; 

 inner lip thickened at the upper part ; opercu- 

 lum horny. Animal, head furnished with two 

 tentacula, having eyes at the base ; foot very 

 short. — There are 9 species recent, and 7 fossil. 



These shells are found in great abundance in 

 the fresh waters of the south of Europe and 

 Africa ; also in Syria, and in the rivers Tigris 

 and Ohio. 



The genus Pirena of Lamarck is now sup- 

 pressed, and the species placed with the above. 



The animal of this family is similar to that 

 of the last ; but the shell is conoid or discoidal, 

 and the margins of the aperture united. All 

 the four genera have opercula, and a thin 

 brownish green epidermis. The animal respires 

 water. 



at the base, and occasionally one also 

 at the upper part of the lip ; spire 



Family 4. — Peristomidce. * 



* Les Peristomiens, Lamarck. 



