MOLLUSCS, VERMES AND HYDROZOA 



adopted by Conchologists and differs materially from that in use prior to 

 the past decade. The classification is in part that of Lang's Textbook of 

 Comparative Anatomy and that of the Academy of Natural Sciences of 

 Philadelphia. Some of the mentioned genera are undesirable in the 

 aquarium and should only find a place in the terrarium or in special aquaria 

 adapted to their study; 



Classification of the Univalves. Freshwater univalves are of 

 two Orders, the Prosabranchia, gilled or water-breathing snails, including 

 the families of the Neritidse, Viviparidae, Valvatidse, Ampularidae, Hy- 

 drobidas and Melanidae in the first Order; and in the second Order the 

 Pulmonata or lung-breathing snails, including most of the land snails and 

 slugs, together with the semi-aqualic family of the Succinea, the aquatic 

 family of the Lymnseidae, comprising the Lymnaea, Planorbes, Segmentina 

 and Ancylus, and the family of the Physidae, comprising the Physa and 

 Aplexa. 



The following classification will briefly describe these orders, families 

 genera and species, and serve as a key to the subsequent descriptions, 

 which are necessarily confined to Eastern and Middle States snails, though 

 the most of them are also common to other sections of the United States. 



Order Prosabranchea — Shell spiral, aperture closed with an operculum, gills internal, 



water-breathing. 



Family Neritidse — Shell semiglobular, aperture closed with an operculum, breathing 



by gills. 



Genus Neritina — N. reclivata, N. showalteri. 



Family Viviparidae — Shell concoidal or discoidal, aperture closed with an operculum, 



gills internal. 



Genus Viviparus — V. viviparus, V. georgianus. 

 Genus Campeloma — C. decisum, C. ponderosus. 

 Genus Lioplax— Z. subcarinata. 

 Family Valvatidse — Shell depressed, aperture rounded, closed with an operculum, 



gills protrusile and plumelike. 

 Genus Valvata — F. tricarinata, V. bicarinata, V. sincera. 

 Family Ampullariidas — Shell globular, depressed at apex, aperture closed with an 



operculum. 

 Genus AmpuUaria — A. depressa, A. miamiensis. 



Family Hydrobiida: — Shell globose or subglobose, apex well defined, operculum 



wingshaped or oval. 



Genus Somatogyrus — S. altilis, S. subglobosus. 

 Genus Amnicola — A. limosa, A. granum. 

 Genus Bithynia — B. tentaculata. 



Family Melaniidje — Shell elongated or conical or fusiform with pointed aperture 



usually subrhomboidal, closed with an operculum. 

 Genus Goniobasis — G. virginica, G. mulineata. 

 Genus Anculosa — A. carinatus. 



