164 
MR.  R.  OWEN  ON  THE  ANATOMY  OF  THE  BRACHIOPODA. 
valve,  or  the  one  which  corresponds  to  the  imperforate  valve  of  Orbicula, 
and  to  the  perforate  valve  of  Terebratula. 
a.  The  shell-secreting  margin  of  the  mantle. 
b.  The  cavity  containing  the  roots  of  the  cilia. 
■       V.  The  same  laid  open. 
c.  The  hranchia. 
d.  The  branchial  vein. 
e.  The  interbranchial  space  of  the  mantle,  which  is  also  vascular. 
/.  The  anterior  muscles,  attached  at  one  extremity  only  to  the  shell. 
g.  The  anterior  pair  of  shell-muscles  analogous  to  the  anterior  shell- 
muscles  of  Orbicula. 
h.  The  third  pair  of  muscles  analogous  to  the  decussating  muscles  of 
the  viscera  in  Orbicula. 
i.  The  posterior  shell-muscle. 
k.  Jc.  The  liver  seen  through  the  mantle. 
1. 1.  The  straight  portion  of  intestine, 
m.  m.  The  ovaries. 
Fig.  16.  A  magnified  view  of  the  respiratory  organs  of  one  of  the  mantle-lobes. 
«,  b,  V,  c,  d,  e,  signify  the  same  parts  as  in  the  preceding  figure. 
17.  Lingula  Semen,  Brod, 
