ME.  HANCOCK  ON  THE  OEGANIZATION  OF  THE  BEACHIOPODA. 
857 
PLATE  LVI. 
Fig.  1.  General  view  of  the  viscera  of  JV.  australis,  the  perivisceral  chamber  completely 
laid  open ; — a,  portion  of  dorsal  pallial  lobe ; b,  peduncle ; c,  c,  capsule  of  ditto  ; 
d,  d,  extremities  of  anterior  and  posterior  occlusors,  those  of  the  right  par- 
tially removed ; d',  ventral  extremities  of  occlusors ; e,  e,  e,  divaricators,  that  of 
the  right  side  divided;  e',  accessory  divaricators ventral  adjustors,  that 
on  the  right  cut  through ; g,  g,  dorsal  adjustors,  cut  through ; h,  peduncular 
muscle ; ^,  oesophagus ; j,  stomach,  with  the  biliary  ducts  exposed  on  the 
right,  the  hepatic  lobes  of  that  side  having  been  removed ; k,  k,  left  hepatic 
lobes  seen  through  the  wall  of  the  perivisceral  chamber ; I,  intestine ; m,  dorsal 
mesentery ; n,  ventral  ditto ; o,  ilio-parietal  band ; portions  of  the  gastro- 
parietal  bands  are  seen  attached  to  the  stomach ; p,  p,  p,  p,  genitalia,  those  of 
the  right  side  have  their  posterior  extremities  removed ; q,  oviduct ; that  on 
the  right  partially  cut  away  so  as  to  expose  the  tubular  portion  of  the  organ 
lying  within  the  anterior  wall  of  the  chamber ; r,  heart,  dilated ; s,  s,  s,  s,  ac- 
cessory pulsatile  vesicles,  also  dilated ; t,  branchio-systemic  vein ; u,  aorta  giving 
otf  dorsal  and  ventral  pallial  arteries ; v,  peduncular  artery ; w,  oesophageal 
ganglia;  w,  loop  of  pallial  nerve  giving  branches  to  mantle,  and  occlusor 
muscles ; g,  pallial  nerves ; z,  z,  peduncular  ditto. 
Fig.  2.  Transv’erse  section  of  the  base  of  the  arms  of  W.  australis: — a,  portion  of  dorsal 
pallial  lobe ; b,  ditto  of  ventral  lobe ; c,  root  of  oesophagus  seen  through  the 
anterior  wall  of  the  perivisceral  chamber ; d,  liver  ditto ; e,  anterior  occlusor 
muscles  ditto ; f,  f,  bases  of  the  lateral  portions  of  the  arms ; g,  g,  ditto  of 
spiral  portions  of  ditto ; h,  membrane  uniting  the  spirals ; i,  i,  great  brachial 
canals  of  ditto ; j,  j,  small  or  etferent  brachial  canal ; k,  k,  great  brachial 
canal  of  lateral  portions,  that  on  the  left  laid  open  to  show  its  connexion 
with  the  same  canal  of  the  spiral ; /,  I,  I,  I,  small  or  efferent  brachial  canals 
of  lateral  portions;  m,  m,  brachial  pouches,  opening  into  the  perivisceral 
chamber ; n,  n,  n,  n,  sheaths  of  calcareous  loop ; o,  o,  o,  grooved  ridge ; p-,p,  p, 
brachial  fold ; q,  q,  cirri. 
Fig.  3.  Transverse  section  of  spiral  portion  of  arm  much  enlarged: — a,  great  brachial 
canal ; b,  small  or  efferent  ditto ; c,  grooved  ridge ; d,  bases  of  cirri ; e,  bra- 
chial fold ; f,  groove ; g,  membrane  uniting  spirals. 
Fig.  4.  Transverse  section  of  genital  organ : — a,  a,  lobules  of  ditto ; b,  genital  or  pallial 
artery;  c,  membrane  suspending  genitalia  in  pallial  sinus ; d,  inner  wall  of  sinus. 
Fig.  5.  Dorsal  view  of  stomach,  exhibiting  the  branchio-systemic  vein  laid  open: — 
a,  oesophagus ; b,  stomach ; c,  commencement  of  intestine ; d,  lateral  gastro- 
parietal  band ; e,  central  ditto ; f,  heart ; g,  dorsal  pallial  artery ; h,  ventral 
ditto  ; i,  branchio-systemic  vein  laid  open ; j,  j,  orifices  leading  into  the  gastric 
or  visceral  lacunes ; k,  hepatic  ducts. 
5 T 2 
