200 



POPULAR CONCHOLOGY. 



and an umbilicus varying in size. Animal, see the de- 

 scription of the family. — Nearly 100 species; also fossil. 



The Mollusca forming this genus are found in the 

 rivers of Africa, India, and South America, but have not 

 been discovered in Europe or North America. Though 

 found generally in rivers, one species, the Ampullaria 

 ovata, inhabits Lake Mareotis, where the water is salt, 

 and another the brackish water near Bio de Janeiro.* 

 In South America they are called ec Idol shells," and the 

 natives hold them in hio4i estimation. Some of the 

 African species have reversed shells, and all that are 

 natives of Africa and America have the operculum horny : 

 those, on the contrary, which come from India, have it 

 usually shelly, and are furnished with an internal groove for 

 its reception parallel to the mouth, which is thickened, f 



The animals possess the peculiarity of a large bag open- 

 ing beneath, and situated on one side of the respiratory 

 organs; this they fill with water, by which means they 

 can exist for a considerable period out of their natural 

 element. Specimens have been brought from Egypt to 

 Paris alive, although packed up in sawdust; and, as a 

 further instance, the following may be adduced. A box 

 sent to M. Caillaud, containing a number of river shells 

 from the Nile, was delayed four months on its road, and 

 when it reached Paris was in such a state, from the putre- 

 faction of the greater part of its contents, that they were 

 all thrown into water. A few hours after a great number 

 of living AmpullaricE, which had been shut up in this mass 

 of putrefaction, were discovered creeping quietly about, 

 and some of them lived four and six months after. They 

 have also been found alive in logs of mahogany brought 

 from Honduras to this country. Laidlay placed some in 

 a drawer to ascertain the limits of their endurance, and 



* Darwin. 



t Swainson, Zoological Illustrations, 



