342 Shell Life 



The shell is more convex above than below, dark 

 brown, not very glossy, the whorls crossed by deep 

 lines. It is a local species, occurring chiefly in the 

 south and west of England, its habitat under logs 

 and dead leaves in woods. The Crystal Snail 

 {H. crystallina) is only one-eighth of an inch across, 

 glossy, thin and translucent, with a greenish tinge. 

 It has a very narrow umbilicus. The animal is 

 greyish white, with the upper tentacles deep black. 

 It occurs about decayed stumps, dead leaves and moss, 

 and under stones, in woods and meadows. The 

 Tawny Glass-snail {Gonnlus fulva) differs from the 

 ^^ Hyalinias in having a pyramidal shell, the 

 ^^^ spire being considerably raised ; there is also 

 Tawny j^ mcrc dcprcssiou (with occasional perfora- 

 tion) instead of an umbilicus. The colour is 

 indicated in the names, and the shell is thin and 

 glossy. Its height and its breadth are equal — about 

 one-tenth of an inch. Its habitat is similar to that 

 of II. crystallina. This species from the form of its 

 shell makes an easy passage to tlie snails described 

 in the next chapter. 



In another respect two species of Hyalinia show 

 affinity with the genus Helix, that is in the 

 development of what has been termed the " love- 

 dart." The species referred to are H. 'ii it Ida and IT. 

 excavata. The instrument consists of a delicate 

 shaft of carbonate of lime, finely-pointed, and con- 

 tained in a pocket of the female organ, whence it is 

 discharged just prior to the union of two individuals, 

 and embedded in the flesh of its mate. It is only to 

 be found in mature snails, and its office apparently is 

 to excite the sexual instinct. 



