GASTROPODA PROSOBRANCHIATA. 47 



divided above, and outer lip thin. Tr. varius L., Adriatic and Mediter- 

 ranean. 



Fam. Neritidae (Neritacea). With thick, hemispherical shell and operculum. 

 Eyes stalked, behind the two long tentacles. Proboscis short, often bilobed. 

 Foot large, triangular. Heart perforated by rectum, with two auricles. Nerita 

 L. Shell thick, hemispherical, spiral lateral ; aperture semi-circular. N. rugata 

 Reel. ; N. (jVeritina') fluvlatilis L. ; Namcella Lam. ; N. elliptica Lam. , 

 Pacific Ocean. 



2. Ptenoglossa. Without siphon, aperture of shell entire, without 

 excavation or canal. Tongue armed with rows of numerous small 

 hooks and without the median plates. 



Fam. Janthinidae. Janthma bicolor Menke, Mediterranean. 

 Fam. Solariidae, (Wentle-traps). Scalarla communis Lam., So. pretiosa, 

 Lam., East Indies. Solarium perspectivum Phil., Mediterranean. 



3. Rhachiglossa. With long proboscis invaginable from the base. 

 Tongue long and narrow with at most three plates in each transverse 

 row, a toothed median plate and an intermediate plate on each side, 

 which are often reduced to mere hooks, and may be absent. All 

 possess a siphon and are predatory. 



Fam. Volutidae (Faltenschnecken). Voluta undulata Lam., New Zealand ; 

 V. vespertilio, East Indies ; Qymbium cetliiopicum L. 



Fam. Olividas. Oliva ntriculus Lam. , Indian Ocean ; Harpa ventricosa 

 Lam., New Guinea. 



Fam. Muricidae (Canaliferae). Murcx brandaris L., Mediterranean. Fusus 

 australis, Quoy Gaim. Columbella mercatoria L.. Atlantic. 



Fam. Buccinidae. Whelks. Buccinum undatnm L. ; Nassa reticulata L. 

 Mediterranean ; Purpura lapillus L., North Sea. 



4. Toxoglossa. Tongue with two rows of long hollow hooks, which 

 can be protruded from the mouth. All possess a siphon, and usually 

 prey on marine animals. 



Fam. Conidae (fig. 520) (Kegelschnecken). Comis litteratiis L., East Indies. 

 Fam. Terebridae (Schraubenschnecken). Terebra dimidiata Lam. 

 Fam. Pleurotomidae. Pleurotoma nodifera Lam. ; Cancellaria Lam. ; C. can- 

 cellata, Lam. 



5. Tsenioglossa. In each transverse row of the elongated radula 

 there are usually seven plates. Two small jaws usually found at the 

 mouth entrance. 



Holostomatous are : 



Fam. Littorinidae, (Winkles). Littorina littorea L. 



Fam. Cyclostomidae. Eespire air like the Pulmonata by vessels of the mantle 

 cavity. Live in damp places on land. Cyclostoma elcgans Drap. 



Fam. Paludinidae, (Flusskiemenschnecken). Inhabit fresh water. Paludina 

 mmpara L. ; P. impura Lam. 



Fam. Vermetidae, (Wurmschnecken). Vermetus arenarius L. 



Fam. Cerithiidae. Cerithium leave Quoy Gaim. 



