ME.  HANCOCK  ON  THE  OEGANIZATION  OF  THE  BEACHIOPODA. 
859 
with  the  roots  of  the  biliary  ducts  exposed,  the  left  lobes  of  the  liver  havinj^ 
been  removed ; r,  right  lobes  of  the  liver  seen  through  the  dorsal  mesentery  ; 
s,  intestine ; t,  portion  of  gastro-parietal  band ; t\  central  ditto ; ventral 
mesentery ; upper  portion  of  ditto ; v,  right  oviduct,  the  left  one  is  almost 
entirely  removed ; iv,  heart ; x,  dorsal  pallial  artery ; y,  ventral  ditto ; y',  blood- 
sinus  in  mesenteric  membrane ; z,  oesophageal  ganglia. 
Fig.  3.  Longitudinal  section  of  peduncle: — a,  distal  extremity;  b,  foreign  matter  adhering 
to  ditto ; c,  horny  sheath ; d,  muscular  mass ; e,  e,  walls  of  capsule ; jf,  f,  walls 
of  perivisceral  chamber ; g,  margin  of  orifice  leading  into  capsule ; h,  pedun- 
cular muscle ; i,  right  ventral  adjustor ; J,  muscular  enlargement  attaching 
ditto  to  peduncle ; k,  right  dorsal  adjustor ; I,  muscular  enlargement  uniting 
the  latter  to  peduncle. 
Fig.  4.  Ventral  aspect  of  peduncle,  the  capsule  laid  open: — a,  peduncle;  b,  muscular 
mass  of  ditto ; c,  horny  sheath  of  ditto ; d,  walls  of  capsule ; e,  margin  of  ori- 
fice leading  into  ditto ; f,  f,  irregular  plications  of  the  inner  surface  of  ditto ; 
g,  extremity  of  peduncular  muscle ; h,  ditto  of  accessory  divaricators ; i,  por- 
tion of  ventral  wall  of  perivisceral  chamber ; j,  ditto  of  dorsal  wall  of  ditto. 
Fig.  6.  One  of  the  setse  from  the  pallial  margin  of  W,  australis,  much  enlarged. 
Fig.  6.  A marginal  seta  of  T.  caput-ser^entis : — a,  follicle  from  which  the  seta  originates  ; 
b,  enlarged  extremity  of  follicle,  containing  red  glandular  matter. 
Fig.  7.  Portion  of  the  same  seta  more  highly  magnified. 
Fig.  8.  Two  marginal  setae  of  lAngula  anatina. 
Fig.  9.  Portion  of  the  same,  greatly  enlarged,  exhibiting  transverse  ridges. 
PLATE  LVIII. 
Fig.  1.  Transverse  section  of  the  brachial  grooved  ridge  of  W.  australis: — a,  base  sup- 
porting cirri ; b,  brachial  fold ; c,  groove ; d,  d,  walls  of  great  brachial  canal ; 
e,  small  or  efierent  ditto ; epithelium ; g,  g,  roots  of  cirri  exhibiting  their 
biserial  arrangement ; h,  expanded  bases  of  ditto,  opening  into  the  efferent 
brachial  canal ; i,  i,  plexus  of  blood-channels  communicating  with  that  in  the 
wall  of  the  great  brachial  canal  ;y,/,  great  brachial  plexus ; Tc,  afferent  brachial 
arteries  leading  fi’om  ditto  into  cirri ; I,  I,  the  same  arteries  passing  up  cirri. 
Fig.  2.  Transverse  section  of  the  same  brachial  grooved  ridge,  exhibiting  its  muscular 
system;  the  letters  up  to  and  including  Ji  correspond  to  those  of  fig.  1: — 
i,  i,  group  of  muscular  fibres  for  elevating  the  cirri ; j,j,  ditto  for  contracting 
the  groove  and  brachial  fold;  ]c,Jc,  ditto,  partially  antagonistic  to  the  last  group, 
and  for  bringing  forward  or  depressing  the  cirri ; I,  I,  thin  layer  of  muscular 
fibres,  from  which  group  Ic  originates ; m,  epithelial  lining  of  efferent  brachial 
canal. 
Fig.  3.  Portion  of  brachial  ridge,  exhibiting  the  orifices  leading  into  the  cirri,  the  wall 
