Gastropoda . 



35 



skin of the back. Some have a large slime-pore at the end of the 

 foot, and others are slightly phosphorescent. Like the Snails, 

 1 hey arc fond of damp localities, and at times become great pests 

 owing to the damage they do to held and garden crops of all kinds. 

 Testacella, which, is found* in this country, differs from the .Slugs 

 in having a small external shell at the posterior end of the body. 

 It is not slimy, and lives underground, feeding upon earthworms. 



Class III. SCAPHOPODA. 



{Case 136.) 



This class consists of but two families — the Dentaliidae and 

 Sipfwnojwdidae. These are marine molluscs with an elongate 



Fig. 26. 



British Tooth-shell. (Dcntaliuni tarentinum.) 

 a. the shell ; b. the animal, removed from its shell ; /. the foot. 



body and tubular shell. The edges of the mantle are united 

 under the foot, forming a tube which, like the shell, is open at 

 both ends. The head bears two lobes which carry numerous 

 filaments ; these are sensory and prehensile in function. The 

 foot is capable of considerable extension and the animal digs 

 itself into the sand with it. 



The shell is shaped rather like an elephant's tusk and its larger 

 orifice is at the anterior or head end. The smaller posterior 

 orifice is usually kept out of the sand or mud when the animal 

 is burrowing. Scaphopods are found in all seas, there being 

 seventeen British species. They are found at all depths down 

 to 2,500 fathoms. Dentalium and Cadulus are the most 

 characteristic genera (Case 130). 



02 



