UNIVALVES BULLA. 61 



lar to those, are land species; they are in form nearly al- 

 lied to the genus Helix : and what is worthy of remark, 

 the animals which inhabit them are oviparous, their 

 young being produced from eggs. The reverse varieties 

 (that is to say, those having their whorls or spires twist- 

 ed contrary to the usual direction, and having, at the same 

 time, their mouths placed on the opposite side) are highly 

 valued. The Bulla Purpurea inhabits Africa, and is 

 found in rice-fields. 



The snail-shaped Bullae, such as the Fasciata, Virginea, 

 &c. &c. are mostly beautifully banded with parti-colored 

 streaks; they are found in the rivers of Asia. The Bulla 

 Gelatinosa, is an inhabitant of the rivers of Denmark. 

 The Fontinalis is found in the Danube, and other species 

 inhabit various lakes and rivers of Europe ; in wet mea- 

 dows, among moss, they are also to be met with. Some 

 species of this genus are remarkable for the brittleness 

 and lightness of their shells; such are the Bulla Velum, 

 Vesica, &c. &c. 



The inhabitant of one of the species. Bulla Lignaria, 

 and in all probability, those of most of the genus, isfuniish- 

 ed with an organ resembling- the gizzard of a fowl, and 

 which it appears to use for the purpose of masticating its 

 food. 



The dififerent species of this genus are to be found in 

 the Mediterranean, African, American, Indian, European, 

 and Northern seas. 



The Bulla, probably, derives its name from some of tlie 

 lesser species resembling a dew-drop, or bubble of water 

 caused by the Tain, 



