ME.  HANCOCK  ON  THE  OEGANIZATION  OF  THE  BEACHIOPODA. 
853 
«,  hinge-plate ; dental  sockets ; c,  hinge-process ; <?,  longitudinal  plate  or 
septum ; e,  crura ; f,  crural  procesess ; g,  upper  or  dorsal  member  of  loop ; 
A,  lower  ditto ; transverse  portion  of  ditto. 
Fig.  5.  Portion  of  dorsal  valve  of  W.  cranium: — a,  dental  sockets;  A,  hinge-process; 
c,  crura  of  loop ; d,  crural  processes ; portion  of  upper  or  dorsal  member  of 
loop  ; f,  impression  of  dorsal  adjustors. 
Fig.  6.  Lateral  half  of  ventral  pallial  lobe  of  Terehratulina  ca^ut-serjpentis,  exhibiting 
arrangement  of  spicula : — a,  marginal  fold ; A,  setse ; c,  spicula  overlying  great 
pallial  sinus ; d,  d,  ditto  overlying  the  branches  of  the  sinus. 
Figs.  7,  8.  Two  spicula  highly  magnified. 
Fig.  9.  Lateral  half  of  ventral  pallial  lobe  of  Megerlia  truncata,  exhibiting  arrange- 
ment of  spicula : — a,  marginal  fold ; A,  genitalia ; c,  c,  spicula. 
Fig.  10.  General  view  of  the  viscera  of  W.  australis,  the  perivisceral  chamber  having 
been  laid  open  from  above: — a,  portion  of  dorsal  pallial  lobe;  A,  ditto  of  ventral 
lobe ; c,  peduncle ; c',  capsule  of  ditto ; d,  extremities  of  anterior  occlusor 
muscles,  that  on  the  right  partially  removed ; d',  ditto  of  posterior  occlusors, 
the  right  one  also  partially  removed ; d!',  ventral  extremities  of  occlusors ; 
e,  divaricators ; d,  extremities  of  the  same  attached  to  cardinal  process ; 
e”,  accessoiy  divaricators;  f,f,  dorsal  adjustors,  cut  through;  g,  ventral 
adjustors ; A,  oesophagus ; ^,  stomach ; j,  intestine ; Jc,  ducts  of  the  right 
hepatic  lobes,  the  latter  ha\ing  been  removed ; K,  anterior  hepatic  lobe  of  the 
left  side,  seen  through  the  wall  of  the  perivisceral  chamber;  posterior- 
ditto  ; I,  lateral  gastro-parietal  band ; m,  central  ditto ; n,  ilio-parietal  ditto  ; 
0,  dorsal  mesentery ; ]p,  ventral  ditto ; g,  laminated  portions  of  oviducts  (auri- 
cles of  the  pseudo-hearts) ; r,  orifice  leading  into  ditto ; s,  s,  s,  s,  genital 
organs,  those  on  the  right  partially  removed ; t,  heart,  dilated ; t\  t',  t',  access- 
ory pulsatile  vesicles ; u,  branchio-systemic  vein  bringing  the  blood  from  the 
arms  or  gills  and  the  rest  of  the  body  to  the  heart ; v,  v,  v,  ventral  pallial  or 
genital  arteries ; v',  v',  dorsal  ditto ; x,  oesophageal  ganglia,  giving  off  nerves. 
PLATE  LIII. 
Fig.  1.  Dorsal  \iew  oi  Terehratulina  caput-serpentis,  deprived  of  the  shell: — a,  pallial 
lobe;  A,  body;  c,  peduncle;  <Z,<Z,  great  pallial  or  genital  sinuses;  ramifications 
of  ditto ; f,  muscular  ties  passing  between  the  walls  of  ditto ; g,  genitalia  seen 
through  the  walls  of  ditto ; A,  marginal  fold ; ^,  setae ; j,  extreme  pallial  mar- 
gin ; k,  depressions  corresponding  to  the  bases  of  the  crura ; I,  ridge  formed 
by  the  union  of  the  pallial  margins ; m,  edge  of  dorsal  mesentery ; n,  n,  liver 
seen  through  the  walls  of  the  perivisceral  chamber ; o,  extremities  of  anterior 
occlusors ; p,  ditto  of  posterior  occlusors ; g,  ditto  of  divaricators ; r,  ditto  of 
dorsal  adjustors. 
