320 



Shell Life 



typical species — the Ram's-horn or Trumpet-snail, so 

 frequently introduced in fresh- water aquaria. Here 

 it will be seen by reference to the illustration, that 

 instead of an elevated spire with the wliorls one 



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Rams-horn Snail, PhDiorhl^ cornevs (nat. size) 



above the other they are all in the same plane, and 

 that the mouth of the shell is to the left instead of 

 on the right as in Liinncea. The spiral is therefore 

 described as dextral, tlie shell discoidal. The animals 



