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placentalia

placentalia


  2  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Placentalia  \Plac`en*ta"li*a\,  n.  pl  [NL.]  (Zo["o]l.) 
  A  division  of  Mammalia  including  those  that  have  a  placenta, 
  or  all  the  orders  above  the  marsupials. 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Mammalia  \Mam*ma"li*a\,  n.  pl  [NL.,  from  L.  mammalis.  See 
  {Mammal}.]  (Zo["o]l.) 
  The  highest  class  of  Vertebrata.  The  young  are  nourished  for 
  a  time  by  milk,  or  an  analogous  fluid,  secreted  by  the 
  mammary  glands  of  the  mother. 
 
  Note:  Mammalia  are  divided  into  three  subclasses;  --  I. 
  {Placentalia}.  This  subclass  embraces  all  the  higher 
  orders  including  man.  In  these  the  fetus  is  attached 
  to  the  uterus  by  a  placenta.  II  {Marsupialia}.  In 
  these  no  placenta  is  formed,  and  the  young,  which  are 
  born  at  an  early  state  of  development,  are  carried  for 
  a  time  attached  to  the  teats,  and  usually  protected  by 
  a  marsupial  pouch.  The  opossum,  kangaroo,  wombat,  and 
  koala  are  examples.  III.  {Monotremata}.  In  this  group 
  which  includes  the  genera  {Echidna}  and 
  {Ornithorhynchus},  the  female  lays  large  eggs 
  resembling  those  of  a  bird  or  lizard,  and  the  young, 
  which  are  hatched  like  those  of  birds,  are  nourished  by 
  a  watery  secretion  from  the  imperfectly  developed 
  mamm[ae].