854 
]\IE.  HAjSTOCK  on  the  oeganization  of  the  beachiopoda. 
Fig.  2.  Ventral  view  of  the  same;  the  letters  up  to^  agree  with  those  of  fig.  1 : — Tc^  ex- 
tremities of  occlusor  muscles;  ditto  of  divaricators ; m,  ditto  of  ventral 
adjustors ; w,  ditto  of  peduncular  muscle ; o,  o,  peduncular  nerves. 
Fig.  3.  Dorsal  view  of  the  animal  of  W.  cranium  :—a,  pallial  lobe ; b,  body ; c,  peduncle ; 
d,  d,  great  inner  pallial  sinus ; e,  outer  ditto ; f,  genitalia,  appearing  through 
the  walls  of  the  sinuses ; g,  marginal  fold ; A,  setae ; i,  cu'cumpallial  vessel ; 
j,  extreme  pallial  margin ; A,  two  lobes  corresponding  to  cavities  at  the  sides 
of  the  foramen;  Z,  similar  lobes  corresponding  to  cavities  in  the  umbonal 
region  of  dorsal  valve ; m,  ridge  resulting  from  the  union  of  the  pallial  mar- 
gins; w,  extremities  of  anterior  occlusors;  o,  ditto  of  posterior  occlusors; 
p,  ditto  of  dorsal  adjustors ; q,  ditto  of  divaricators. 
Fig.  4.  Ventral  view  of  the  same;  the  letters  up  to  A as  in  fig.  3: — Z,  extremities  of 
occlusor  muscles ; m,  ditto  of  divaricators ; m',  portions  of  ditto  corresponding 
to  the  accessory  divaricators ; w,  ditto  of  ventral  adjustors ; o,  ditto  of  pedun- 
cular muscle;  p,p,  peduncular  nerves. 
Fig.  5.  General  view  of  perivisceral  chamber  of  T.  caput-serpentis  seen  from  above 
a,  portion  of  dorsal  pallial  lobe ; h,  peduncle ; c,  capsule  of  ditto ; d,  ridge 
formed  by  the  union  of  the  pallial  margins ; e,  stomach ; f,  intestine ; g,  g,  late- 
ral lobes  of  the  liver ; A,  laminated  portions  of  o-viducts ; i,  orifices  leading  into 
ditto ; y,  anterior  occlusor  muscles ; A,  posterior  ditto ; Z,  Z,  Z,  dorsal  adjustors 
cut  through ; m,  ventral  ditto ; n,  divaricators ; n\  extremities  of  ditto  attached 
to  cardinal  process ; o,  dorsal  mesenteiy ; p^  ventral  ditto ; q^  lateral  gastro- 
parietal  bands ; r,  ilio-parietal  bands ; s,  heart,  dilated ; t,  accessory  pulsatile 
vesicle ; u,  branchio-systemic  vein ; -y,  ventral  pallial  artery ; iv,  dorsal  ditto  ; 
X,  peduncular  artery. 
Fig.  6.  Enlarged  view  of  a portion  of  the  mantle  of  Megerlia  truncata^  exhibiting  the 
spicula  undisturbed : — a,  «,  spicula. 
Fig.  7.  One  of  the  spicula  more  highly  magnified. 
Fig.  8.  Much  enlarged  view  of  a portion  of  the  genitalia  of  W.  australis : — a,  pallial  mem- 
brane ; h,  h,  yellow  ovigerous  substance ; c,  c,  red  matter  supposed  to  be  the 
male  secreting  organ. 
Fig.  9.  Oviduct  of  JV.  cranium  as  seen  through  the  wall  of  the  perhisceral  chamber : — 
a,  portion  of  genital  organ ; h,  genital  or  pallial  artery ; c,  mtemal  laminated 
portion  of  oviduct ; tZ,  tubular  portion  of  ditto ; external  orifice. 
Fig.  10.  Oviduct  of  W.  australis’. — a,  portion  of  anterior  wall  of  permsceral  chamber; 
5,  ditto  of  ilio-parietal  band;  c,  laminated  portion  of  oviduct  (amide  of 
pseudo-heart) ; d,  orifice  leading  into  ditto  from  peridsceral  chamber ; e,  tubu- 
lar portion  of  organ ; _/*,  external  orifice  seen  through  the  wall  of  the  chamber ; 
g,  ventral  pallial  artery ; A,  accessory  pulsatile  vesicle  in  contracted  state. 
