858 
ME.  HANCOCK  ON  THE  OEGANIZATION  OE  THE  BEACHIOPODA. 
Fig.  6.  Anterior  or  dorsal  aspect  of  root  of  oesophagus,  showing  the  connexion  of  the 
branchio-systemic  vein  with  the  great  oesophageal  lacunes : — a.  outer  sheath  of 
oesophagus ; 5,  muscular  wall  of  ditto ; c,  mucous  membrane  of  ditto ; d,  ven- 
tral mesentery ; large  sinus  between  the  layers  of  ditto ; /,  f,  dorsal  pallial 
nerves ; g,  oesophageal  collar ; h,  h,  etferent  brachial  canals ; 2,  efferent  bra- 
chial sinuses ; j,  two  tubercles  on  the  walls  of  ditto,  function  unknown  ; 
Jc,  great  oesophageal  lacunes ; I,  branchio-systemic  vein  laid  open. 
Fig.  7.  Enlarged  view  of  the  heart  attached  to  the  stomach : — a,  stomach ; h,  commence- 
ment of  intestine ; c,  lateral  gastro-parietal  band ; d,  central  ditto ; e,  dorsal 
mesentery ; heart  in  contracted  state ; g,  branchio-systemic  vein  opened  to 
show  its  connexion  with  the  heart ; A,  aorta ; i,  dorsal  pallial  artery ; ven- 
tral ditto ; A,  portion  of  oviduct. 
Fig.  8.  Portion  of  lateral  gastro-parietal  band,  exhibiting  blood-channels  or  lacunes : — 
a,  dorsal  pallial  artery ; lacunes  between  the  layers  of  membrane ; c,  c,  the 
two  layers  composing  the  band. 
PLATE  LVII. 
Fig.  1.  Posterior  view  of  the  viscera  of  W.  australis^  the  umbonal  region  ha\ing  been 
removed: — «,  dorsal  surface  of  animal ; A,  ventral  ditto ; c,  anterior  occlusors ; 
c',  posterior  ditto  ; c",  ventral  extremities  of  occlusors ; d,  divaricators ; d',  ac- 
cessory ditto ; e,  ventral  adjustors ; f,  f,  portions  of  dorsal  ditto ; g,  stomach, 
the  liver  having  been  removed  from  the  left  side,  the  roots  of  the  hepatic  ducts 
are  exposed ; A,  right  hepatic  lobes ; 7,  intestine ; j,  j,  lateral  gastro-parietal 
bands ; the  central  band  is  seen  immediately  above  the  heart ; k,  fissure  corre- 
sponding to  the  longitudinal  plate  or  septum  of  the  dorsal  valve ; Z,  upper 
portion  of  ventral  mesentery ; m,  m,  genitalia ; w,  oviducts,  attached  to  the 
intestine  by  the  ilio-parietal  bands ; o,  heart  in  contracted  state,  griing  off 
two  lateral  arteries ; j?,  accessory  pulsatile  vesicles ; g,  ventral  pallial  arte- 
ries ; r,  peduncular  artery ; s,  orifices  for  the  passage  of  the  crma  of  the  loop ; 
Z,  brachial  cirri ; m,  orifices  leading  into  inner  pallial  sinuses ; v,  outer 
dorsal  pallial  sinus  partially  laid  open ; w,  ventral  ditto,  ditto. 
Fig.  2.  Lateral  view  of  the  viscera  of  the  same:-— a,  dorsal  surface  of  animal;  A,  ventral 
ditto ; c,  c,  anterior  wall  of  perivisceral  chamber ; d,  brachial  sphal,  the  left 
lateral  portion  of  the  arm  having  been  removed;  d\  right  lateral  portion  of  ditto; 
e,  great  brachial  canal ; y,  small  or  efferent  ditto ; g,  brachial  grooved  ridge ; 
A,  sheath  of  transverse  portion  of  calcareous  loop ; i,  i,  dorsal  extremities  of 
anterior  and  posterior  occlusors ; j,  ventral  portion  of  ditto ; A,  divaricators ; 
A',  accessory  ditto ; A'',  extremities  of  ditto  attached  to  cardinal  process ; 
Z,  Z,  portions  of  ventral  adjustors ; Z',  Z',  portions  of  dorsal  ditto ; w^,  peduncle ; 
w,  peduncular  capsule;  o,  peduncular  muscle;  p,  oesophagus;  stomach. 
