28 



SHELL GALLERY. 



Case 186. 



The eggs of Land-Snails vary in texture, size, and in numbers ; 

 they are usually white, but in some instances yellow and pale green. 

 Those of some of the large South- American forms are as hard as 

 that of a hen, and more than an inch in length (Case 120). 



Slugs (Cases 106, 107) are very like Snails without external shells ; 

 most of them, however, possess a small internal shelly plate, or a few 



Fig. 23. 



Fis:. 24. 



British Land-Snail {Helix pomatia). 

 a, eye-bearing tentacles (" horns ") ; h, lower or smaller tentacles. 



calcareous granules hidden beneath the skin of the back. Some have 

 a large slime-pore at the end of the foot, and others are slightly 

 phosphorescent. Like the Snails, they are fond 

 of damp localities, and at times become great 

 pests to farmers in devouring the young shoots 

 of the growing corn. Testacella, which is found 

 in this country, differs from the Slugs in having 

 an external shell at the tail-end of the foot. 

 It is not slimy, and lives under ground, feeding 

 upon earthworms. 



Class IIL— SCAPHOPODA.* 



The "Tooth-shells" {Dentaliidce) form a 

 distinct group, the shells of which are very 

 unlike those of any other mollusc, but closely 

 resembling the shelly tubes constructed by 

 certain kinds of marine worms. The Dentalia 



* From the Greek: scaphe, a small boat, and pons, 

 a foot— the foot of some Scaphopods being somewhat 

 pointed like the prow of a vessel. 



British Tooth-shell 

 (Dentalium tarentinum). 



a. The shell, b. The an- 

 imal, removed from 

 its shell ; •/ the foot. 



