The  shell  is  developed  upon  the  young,  while  still  in  the
embryo  ^tate.
^2:^^-x><^^


HELICIDA.  149


Family  IIL  HELICIDiE.
BoBT  long  and  spirally  coiled :  mantle  covering  the  front  or
anterior  part :  tentacles  nearly  always  4  (rarely  2  only),  re-
tractile :  eyes  placed  on  the  tips'  of  the  upper  or  single  pair ;
Joat  oblong,  distinct  from  the  rest  of  the  body.
Shell  spiral,  and  in  almost  every  case  capable  of  containing
•the  whole  body.
