GASTEROPODA. 139 



Animal with a long incui-rent siphon, formed by the left neck-lappet ; 

 left gill developed, but much smaller than the right* ; muzzle produced into 



Fig. 84.t 



two long tentacular processes ; tentacles extremely elongated, slender. Inha- 

 bits lakes and rivers throughout the warmer parts of the world, retiring deep 

 into the mud in the dry season, and capable of surviving a drought, or removal 

 from the water for many years. In the lake Mareotis, and at the mouth of 

 the Indus, ampullariee are abundant, mixed with marine shells. Their eggs 

 are lai'ge, inclosed in capsules, and aggregated in globular masses. 



Distr., 50 sp. S. America, West Indies, Africa, India. 



Suh-genera. Pomiis, Humph. A. ampullacea. Operc. horny. 



Marisa, Gray (ceratodes, Giulding). A. cornu-arietis PI. IX., fig. 31. 

 Operc. horny. Shell discoidal. 



Asolene, D'Orb. A. platse. Animal without a respiratory siphon ; operc. 

 shelly. Distr., S. America. 



Lanistes, Montf. A. bolteniana, L., PI. IX., fig. 32. Shell reversed, 

 umbilicated, peristome thin ; operc. horny. Distr., W. Africa, Zanzibar, 

 Nile. 



Meladomus, Sw. Paludina oLivacea, Sby. Shell reversed, imperforate ; 

 peristome thin ; operc. horny. 



? Amphibola, Schumacher. 

 Syn., ampullacera, Quoy. Thallicera, Sw. 



* The ampullaria is said to have a pulmonic sac in addition to its gills (Gray, 

 Owen), but we have not met with specimens sufficiently well preserved to exhibit it. 



would be very desirable to examine the amp. cornu-arietis, in which, probably, 

 the gills are symmetrical, as in the cephalopods. 



t Fig. 84. Ampullaria canaliculata, Lam. (from D'Orb.) South America. The 

 branchial siphon {s) is seen projecting from the left side ; o, operculum 



