2  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Lamellibranchia  \La*mel`li*bran"chi*a\,  Lamellibranchiata 
  \La*mel`li*bran`chi*a"ta\,  n.  pl  [NL.  See  {lamella},  and 
  {Branchia},  {Branchiate}.]  (Zo["o]l.) 
  A  class  of  Mollusca  including  all  those  that  have  bivalve 
  shells,  as  the  clams,  oysters,  mussels,  etc 
 
  Note:  They  usually  have  two  (rarely  but  one)  flat, 
  lamelliform  gills  on  each  side  of  the  body.  They  have 
  an  imperfectly  developed  head,  concealed  within  the 
  shell,  whence  they  are  called  {{Acephala}}.  Called  also 
  {Conchifera},  and  {Pelecypoda}.  See  {Bivalve}. 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Acephala  \A*ceph"a*la\,  n.  pl  [NL.,  fr  Gr  ?,  adj  neut.  pl., 
  headless.  See  {Acephal}.]  (Zo["o]l.) 
  That  division  of  the  Mollusca  which  includes  the  bivalve 
  shells,  like  the  clams  and  oysters;  --  so  called  because  they 
  have  no  evident  head.  Formerly  the  group  included  the 
  Tunicata,  Brachiopoda,  and  sometimes  the  Bryozoa.  See 
  {Mollusca}. 

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