VITRINID^E. 133 



grass, and moss ; they are very lively animals, frequently in 

 motion, and when touched will sometimes jump several inches 

 from the ground. Like the slugs, they are occasionally car- 

 nivorous. 



About 100 species have been described, but on account of the 

 uniformity of their general character, some of these are doubt- 

 less nominal. The distribution is almost universal, but the 

 animal in most of the species of tropical countries is still un- 

 known to us, and many of these may prove to belong to the 

 genus Helicarion or to some group intermediate between that 

 genus and Yitrina. The typical Vitrinas are natives of temper- 

 ate or boreal regions of the northern hemisphere, or of mountain 

 heights in its warmer countries, and are capable of withstanding 

 a low temperature, even crawling about on the surface of the 

 snow. They first occur fossil in the eocene formation of Europe. 

 The typical Vitrinas have been divided into four sections : 



* Shell imperf orate. 



Section SEMILIMAX, Stabile, 1859. Animal not able to with- 

 draw entirely within its shell ; the mantle much developed. Shell 

 oval-elongated. 



Section PHENACOLTMAX, Stabile, 1 859. Animal capable of entire 

 retraction, forming a vitreous epiphragm ; mantle moderately 

 developed. Shell oval. 



** Shell narrowly perforate. 



Section OLIGOLIMAX, Fischer, 1878. Mantle scarcely extending 

 beyond the shell in front ; the animal capable of complete with- 

 drawal. Shell striated, orbicular. 



Section GALLANDIA, Bourgnignat, 1880. Animal wholly re- 

 tractile. Shell conoidal, the last whorl angular ; umbilicus 

 subperforated. 



Genus YITRINOIDEA, Semper, 1873. 



Shell depressed globose, almost membranous, entirely con- 

 cealed by the mantle-lobes. Foot elongated, tail without mucous 

 pore. Jaw smooth, marginal teeth tricuspid (PI. 29, fig. 4). 



Philippines. 



