162 UNIVALVES HELIX. 



woods of Europe, and was first introduced into this 

 country by Sir Kenelm Digby, for medical purposes. 

 The animal (which was considered a luxury by the 

 Romans) is oviparous, and very tenacious of life; to- 

 wards winter it covers its aperture with a calcareous 

 lid, resembling an operculum, and remains in a torpid 

 state until the spring-. 



The shells of the fourth division have a ventricose 

 form, and resemble those of the sixth division of the 

 genus Bulla, as is there observed. The H. ovalis 

 and H. oblonga are the most characteristic ; the eggs 

 of the animal are perfectly elliptical, and are nearly 

 the size of those of the common sparrow. 



The H. amarula of the fifth division is the only co- 

 ronated species of the genus. 



The shells of the sixth division are very globose, and 

 have their Avhorls much produced : the H. ampullacea 

 may be referred to as an example. 



The animal of the H. ianthina, of the eighth divi- 

 sion, has the property of emitting a phosphorescent 

 light, and stains the hand of a purple color, not easily 

 removed : they are found in great numbers, floating on 

 marine substances. 



The eleventh division contains those species which 

 are usually found in stagnant waters ; they have a ven- 

 tricose form, and are remarkably fragile and pellucid. 



This genus has also its turreted class, forming the 

 twelfth division. The H. decollata and H. columna are 

 illustrative of the two families. 



The most rare and beautiful species are the H.ringens, 

 H. tricarinata, H. otis, H. heemastoma, and H. columna. 



There are many species of this genus which inhabit 



