510 GEOGRAPHICAL ZOOLOGY. [paPwT iv. 



Family 12.— LI'LTORIXID.E. (0 Genera, 310 Species.) 



Distribution. — Tlie Littorinidie are niDstly fouml on the coasts 

 in shallow water ; as the eounnon Periwinkle {Littorina litturca)- 

 They are of world-wide distribution ; but Solarium and Phonis 

 are tropical; while Lacuna, Skciica, and most species of Bissoa 

 are Northern. About ISO species are fossil, ran;^ing from the 

 I'ermian to the I'liocene formations. 



Family i;3.-rALUDINlD.F:. (4 Genera, 217 Species.) 



DiSTiJiBUTiON. — The Paludinidie, or Eiver-snails, are all fresh- 

 water, and range over the whole world, raladliia (00 sp.), is 

 confined to the Northern Hemisphere; Am^Jullaria. (136 sp.), 

 is tropical ; Amphibola (3 sp.), inhabits New Zealand and the 

 Pacific Islands ; Valvata (IS sp.), North America and Britain. 

 There are 72 fossil species of Paludina and Valvata, in the 

 AVeahlen formation and more recent fresh-water deposits. 



Family 14.— NEPJTID.E. (10 Genera, 320 Species) 



Distribution. — All warm seas, ranoing north to Norway and 

 the Caspian Sea. Kcritina and A^ari cell a inhabit fresh or brack- 

 ish waters, the latter confined to the countries bordering the 

 Indian Ocean and the islands of the Pacific. Thei'e are 80 fossil 

 species, from the Trias, Lias, and Eocene formations down to 

 recent deposits. 



Family IT..— TUPBIXID.E. (10 Genera, 425 Species). 



DiSTi.iBUTiON. — The genus Troclms (200 sp.) has a world-wide 

 range, but the other genera are mostly tropical, and are most 

 abundant in the Indian and Pacific Oceans. There are more 

 than 900 fossil species, found in all parts of the world, from the 

 Lower Silurian td the Terliarv foi'nnitions. 



