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 occasional!}' car- 

 nivorous. 



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

 uniformit}' 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 man}' of these may prove to belong to the 

 genus Helicarion or to some group intermediate between that 

 genus and Vitrina. The typical Yitrinas 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 t} T pical 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, 1859. Animal capable of entire 

 retraction, forming a vitreous epiphragm ; mantle moderately 

 developed. Shell oval. 



** Shell narrowly perforate. 



Section OLTGOLIMAX, Fischer, 1878. Mantle scarcety extending 

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

 drawal. Shell striated, orbicubr. 



Section GALLANDIA, Bourguignat, 1880. Animal wholly re- 

 tractile. Shell conoidal, the last whorl angular ; umbilicus 

 subperforated. 



Genus YITRINOIDEA, Semper, 1813. 



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. 



