
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 Untvatves. Freshwater univalves are of 
two Orders, the Prosabranchia, gilled or water-breathing snails, including 
the families of the Neritide, Viviparide, Valvatide, Ampularide, Hy- 
drobide and Melanide 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-aquatic family of the Succinea, the aquatic 
family of the Lymnezide, comprising the Lymnea, Planorbes, Segmentina 
and Ancylus, and the family of the Physidz, 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. 
Orper ProsasrancHEA—Shell spiral, aperture closed with an operculum, gills internal, 
water-breathing. 
Family Neritida—Shell semiglobular, aperture closed with an operculum, breathing 
by gills. 
Genus Neritina—W. reclivata, N. showalteri. 
Family Viviparida—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—L. sudcarinata. 
Family Valvatide—Shell depressed, aperture rounded, closed with an operculum, 
gills protrusile and plumelike. 
Genus Valvata—V. tricarinata, V. bicarinata, V. sincera. 
Family Ampullariida—Shell globular, depressed at apex, aperture closed with an 
operculum. 
Genus Ampullaria— A. depressa, A. miamiensis. 
Family Hydrobiide—Shell globose or subglobose, apex well defined, operculum 
wingshaped or oval. 
Genus Somatogyrus—S. a/tilis, S. subglobosus. 
Genus Amnicola—/. /imosa, A. granum. 
Genus Bithynia—B. tentaculata. 
Family Melaniida—Shell elongated or conical or fusiform with pointed aperture 
usually subrhomboidal, closed with an operculum. 
Genus Goniobasis—G. virginica, G. mulineata. 
Genus Anculosa— J. carinatus. 
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