40 BRITISH MOLLUSKS. 



The shell varies from a bright crystalline pale green to a rather 

 muddy yellow, and is composed of from three to three and a half 

 rapidly increasing whorls, smooth and shining, but still showing fine 

 pencil lines of growth, The spire is scarcely raised ; the suture is in- 

 dicated by a delicate linear groove. Authors are somewhat divided in 

 opinion as to the. animal being able to retire into its shell. M. Mo- 

 quin-Tandon separates the six French species into two groups, 

 Hyalina and Helicolimax, characterizing the animal of the first as 

 not wholly withdrawing itself into the shell, and forming no epi- 

 phragm ; of the second, as being able wholly to withdraw, especially 

 on the approach of winter, and close itself in by a vitreous epiphragm. 

 V. pellucida he includes in the latter section, and yet Mr. Berkeley, 

 who has observed this mollusk with great attention, and published 

 its anatomy in the ' Zoological Journal,' writes me word, " the 

 animal never retires completely into its shell." 



Vitrina pellucida is common in all parts of the British Isles. It 

 is a hvely little mollusk, keeping the reflected lobe of its mantle in 

 constant motion over the shell. Mr. Thompson, speaking of its 

 habitats in Ireland, remarks, that in suitable localities it may be 

 found under the first stones to be met with in going inland from the 

 seashore to as great an altitude in the mountain glens as there are 

 moss and leaves to shelter it ; and it is found as far north as Green- 

 land. The United States species, which was thought at first to be 

 identical with our own, is more globose. 



Succinea putris. 



Genus II. SUCCINEA, Draparnaud. 



Animal ; body oblong, swollen, granulated, bearing a very thin 

 capaciously inflated shell, head broad and obtuse, tentacles 

 stout, somewhat cylindrical, lower pair very short, foot acu- 

 minated posteriorily. 



Shell ; imperforate, oblong-ovate, with the spire more or less exserted, 



