MR.  R.  OWEN  ON  THE  ANATOMY  OF  THE  BRACHIOPODA.  161 
Fig.  10.  A  small  portion  of  one  of  the  arms,  magnified. 
11.  A  small  portion  of  the  edge  of  the  mantle,  highly  magnified. 
a.  The  branchial  cilia. 
/3.  The  marginal  fringe. 
y.  The  marginal  canal. 
8.  The  branchial  artery, 
€.  The  branchial  vein. 
t.  Ova. 
12.  The  alimentary  canal,  as  seen  from  above  or  behind,  and  a  portion  of  the 
liver  of  Terebratula  psittacea,  Brug.,  magnified, 
a.  The  mouth. 
/3.  The  oesophagus. 
y.  The  stomach,  with  the  parietes  imperfect  where  the  liver  has  been  re- 
moved :  it  is  turned  tow^ards  the  left  side,  to  show 
The  intestine, 
e.  The  anus. 
t.  A  portion  of  the  liver. 
13.  A  few  of  the  hepatic  folhcles,  highly  magnified,  showing  the  vascular  net- 
work upon  their  parietes  formed  by  the  hepatic  vessels. 
14.  Terebratula  psittacea,  with  the  greater  part  of  the  imperforate  valve  removed 
to  show  the  soft  parts. 
14*.  Terebratula  psittacea,  with  the  perforate  valve  and  lobe  of  the  mantle  re- 
moved to  show  the  arms,  one  of  which  has  been  artificially  unfolded. 
15.  Terebratula  Sowerbii,  King,  natural  size:  the  greater  part  of  the  perforate 
valve  has  been  removed  to  show  the  ova  accompanying  and  obscuring  the 
branchial  vessels,  seen  through  the  mantle. 
16.  The  separated  valves  of  Terebratula  Sowerbii:  in  the  imperforate  valve  the 
arms,  and  one  lobe  of  the  mantle  have  been  removed,  to  show  the  cal- 
careous loop,  visceral  mass,  muscles  and  ova,  surrounding  the  vessels  of 
the  opposite  mantle-lobes. 
The  following  letters  indicate  the  same  parts  in  each  figure. 
a.  The  mantle-lobe  of  the  imperforate  valve. 
b.  The  mesial  fissure,  corresponding  to  the  mesial  process  of  that  valve. 
c.  The  mantle-lobe  of  the  perforate  valve. 
d.  d.  The  fringed  margins  of  the  mantle. 
e.  The  tubular  prolongation  accompanying  the  pedicle. 
/.  /.  The  anterior  pair  of  muscles  arising  from  the  imperforate  valve. 
g.  g.  The  posterior  pair  of  muscles  arising  from  the  imperforate  valve. 
g  .  g  .  Fig.  16.  The  insertion  of  these  muscles  into  the  pedicle. 
h.  h.  The  anterior  pair  of  muscles  arising  from  the  perforate  valve. 
