AMPULLARIA. 345 



the left side in front ; left gill rudimentary ; mantle- 

 cavity with a large pulmonary sac on each side. Rectum 

 not traversing the heart. Foot simple. 



Operculum annular, regular. 



Shell spiral, turbinate, covered with an olivaceous epi- 

 dermis; aperture simple in front. 



The Ampullariid(B are fluviatile, and represent, in the 

 ponds and rivers of the tropics, the Viripandie of more 

 temperate climates. Although distinct gills exist, the 

 respiratory cavity is very large and partly closed, so as 

 to enable these animals to live a long time out of water; 

 in fact, they appear to be truly amphibious, and to be 

 enabled to survive a long drought, and have been known 

 to revive after having been kept several years out of 

 water. The long siphonal tube appears to be formed by 

 the left neck-lappet, which is seen in the Viviparidce in a 

 rudimentary state. 



Genus AMPULLAEIA, Lamarck. 



Respiratory siphon elongate. 



Opei'culum horny, with an external shelly coat. 



Shell globose, umbilicated; spire small, last whorl 

 ventricose ; aperture oblong, entire, peristome continuous, 

 slightly reflexed, with an internal thickened rim or ledge. 



Syii. ? Pila, Bolt., not Klein. Ampullarius, Monlf. 

 Pomacea, Perry. Pachystoma, Guild., not Blnni. Pa- 

 chylabra, Swains. 



E.v. A. fasciata, Gray, pi. 37, fig. 1. Operculum, 

 A. ampullacea, LinncB?is, fig. 1, a, 1, b. Shell, A. am- 

 pullacea, fig. \, c. 



In this genus the aperture of the shell has a thickened 

 callous ledge just within the peritreme to serve as a 



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