856 
ME.  HAJS'COCK  ON  THE  OEGANIZATION  OE  THE  BEACHIOPODA. 
PLATE  LV. 
Fig.  1.  Animal  of  W.  australis  deprived  of  the  shell,  and  the  pallial  lobes  tamed  back 
so  as  to  expose  the  brachial  apparatus  and  anterior  wall  of  the  body : — a,  por- 
tion of  ventral  lobe ; dorsal  ditto ; c,  c,  genitalia  appearing  through  the 
walls  of  the  pallial  sinuses;  d,  base  of  membrane  suspending  genitalia; 
e,  e,  umbonal  region ; f,  peduncle ; g,  spiral  portion  of  brachial  apparatus ; 
A,  lateral  portions  of  ditto ; cirri ; j,  brachial  fold,  a few  cmi  having 
been  removed  to  expose  it  and  the  anterior  wall  of  the  body ; Jc,  position  of 
mouth,  which  is  concealed  under  the  fold ; /,  occlusor  muscles  seen  through 
the  anterior  wall ; w,  left  oviduct  lying  -svithin  the  anterior  wall ; n,  orifice 
leading  into  oviduct. 
Fig.  2.  View  of  brachial  apparatus  and  anterior  wall  of  the  body  of  Terehratulina 
caput-serpentis : — «,  portion  of  ventral  pallial  lobe ; h,  ditto  of  dorsal  lobe ; 
c,  c,  genitalia,  seen  through  the  walls  of  the  pallial  sinuses ; d,  base  of  suspend- 
ing membrane  of  genitalia  forming  a reticulated  line ; e,  muscular  ties  uniting 
the  walls  of  pallial  sinuses ; jf,  umbonal  region ; g,  peduncle ; A,  lateral  por- 
tions of  arms ; ^,  spiral  portions  of  ditto ; p cirri ; A,  A,  roots  of  cmi  that  have 
been  removed ; /,  brachial  fold ; m,  groove  formed  by  ditto ; n,  mouth ; 
0,  occlusor  muscles  appearing  through  the  anterior  Avail ; p,  divaiicators  ditto ; 
ventral  adjustors  ditto ; r,  liver  ditto ; s,  right  oviduct  ditto;  t,  orifice  lead- 
ing into  oviduct. 
Fig.  3.  View  of  brachial  apparatus  and  anterior  wall  of  the  body  of  Idlignclionella  psit- 
facea : — a,  ventral  pallial  lobe ; b,  dorsal  ditto ; c,  c,  genitalia  imperfectly  deve- 
loped ; d,  base  of  suspending  membrane  of  ditto  appearing  as  a reticulated 
line ; e,  muscular  ties  passing  between  the  walls  of  the  genital  sinuses ; f\  um- 
bonal portion  of  animal ; g,  peduncle ; h,  the  left  arm  partially  uncoiled ; 
base  of  the  right  arm,  the  arm  itself  having  been  removed ; j,  chri ; A,  bra- 
chial fold ; I,  mouth ; m,  occlusor  muscles,  seen  through  the  anterior  wall ; 
n,  divaricators  ditto  ; o,  liver  ditto ; p,  oesophagus  ditto  ; edge  of  dorsal  me- 
sentery ditto ; r,  r,  r,  r,  oviducts  ditto ; s,  orifices  leading  mto  oAiducts. 
Fig.  4.  Transverse  section  of  root  of  oesophagus  of  W.  australis,  exhibiting  the  great 
oesophageal  blood-lacunes : — a,  a,  base  of  arms ; b,  b,  efferent  brachial  sinuses  ; 
c,  two  tubercles  on  the  walls  of  ditto,  function  not  ItnoAAm;  d,  d,  efferent 
brachial  canals ; e,  dorsal  mesentery ; f,  ventral  ditto ; g,  mucous  membrane 
lining  oesophagus ; A,  muscular  wall  of  oesophagus ; ^,  outer  sheath  of  ditto ; 
j,  j,  great  oesophageal  lacunes ; A,  large  sinus  Avithin  the  layers  of  the  me- 
senteric membrane ; I,  portion  of  the  central  oesophageal  ganglion ; m,  m,  roots 
of  dorsal  pallial  nerves ; n,  oesophageal  collar. 
