GASTEEOPODA. 



139 



Animal with a long inciu'rent siplion, 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 diy 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, ampullariffi are abundant, mixed with marine shells. Their eggs 

 are large, inclosed in capsules, and aggregated in globular masses. 



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



Sub-genera. Pomus, Humph. A. ampuUacea. Operc horny. 



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

 Operc. homy. SheU discoidal. 



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

 shelly. Distr., S. America. 



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

 umbilicated, peristome thin ; operc. horny. Distr., "W. Africa, Zanzibai-;, 

 NHe. 



Meladomv^, Sw. Paludina olivacea, Shy. Shell reversed, imperforate • 

 peristome thin ; operc. horny. 



? Amphibola, Schumacher. 

 Syn., ampuUacera, 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. 

 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. Ampul'aria canaliculata. Lam. (from D'Orb.) South America. The 

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



