MR.  R.  OWEN  ON  THE  ANATOMY  OF  THE  BRACHIOPODA. 
157 
arteries  to  near  the  hearts,  beyond  which  I  could  not  trace  them.  I  can  speak  posi- 
tively that  there  is  no  longitudinal  ganglionic  cord  on  either  aspect  of  the  viscera, 
corresponding  to  the  nervous  system  of  the  Cirripeds.  A  single  small  ganglion  is  situ- 
ated on  the  opposite  side  of  the  oesophagus,  but  on  a  plane  posterior  to  the  preceding. 
This,  however,  I  suspect  to  be  the  cerebral  ganglion,  and  believe  it  gives  off  the  nerves 
to  the  free  spiral  extremities  of  the  arms,  close  to  the  base  of  which  it  is  situated. 
Some  Observations  on  the  Anatomy  o/Lingula  Audebardii,  Brod. 
The  structure  of  this  species  corresponds  in  all  essential  particulars  with  that  of  Ling, 
anatina  as  given  by  Cuvier.  The  differences  appear  first  in  the  length  of  the  cilia, 
which  in  the  present  species  are  three  or  four  times  longer  than  those  of  Ling,  ana- 
tina. The  subdivisions  of  the  branchial  vessels  project  from  the  inner  surface  of  the 
mantle,  in  linear  series  similar  in  their  direction  to  those  of  Ling,  anatina :  but  the 
lines  are  not  continuous ;  they  are  composed  of  distinct  and  separate  folds  of  the 
mantle,  of  a  minute  size,  along  the  convexity  of  each  of  which  a  single  vascular  loop 
is  extended  without  giving  off  lateral  ramulets,  the  whole  structure  affording  a  beautiful 
example  of  the  first  stage  in  the  composition  of  a  complex  lamellated  gill'. 
All  the  glandular  masses  communicating  with  the  alimentary  canal  bear  the  green 
colour  characteristic  of  the  liver,  especially  that  central  one  surrounding  the  stomach, 
which  Cuvier  has  marked  as  the  salivary  gland  in  Ling,  anatina.  Now  as  the  speci- 
mens examined  by  that  great  anatomist  had  been  long  preserved  in  spirit,  one  of  them 
having  in  fact  formed  part  of  the  collection  of  Seba,  the  colour  of  the  parts  had  pro- 
bably been  discharged.  I  am  therefore  inclined  to  think  that  Ling,  anatina  agrees  in 
this  respect  both  with  the  newly  added  species  of  the  same  genus,  and  with  the  other 
Brachiopodous  genera,  and  indeed  exhibits,  in  the  absence  of  salivary  glands,  as  of 
dental  organs,  a  correspondence  with  all  the  Acephalous  Mollusks.  With  respect  to 
Ling.  Audebardii,  L  shall  only  add,  that  the  distal  end  of  its  pedicle  is  dilated  and 
rounded,  and  in  the  small  specimen  dissected  did  not  present  any  appearance  of  having 
been  attached  to  a  foreign  substance. 
General  Remarks. 
On  comparing  together  the  three  genera  of  Brachiopoda  above  described,  we  find 
that  although  Orbicula  in  the  muscular  structure  of  its  arms,  and  the  proportion  of  the 
shell  occupied  by  its  viscera,  is  intermediate  to  Lingula  and  Terebratula,  yet  that  in  the 
structure  of  its  respiratory  organs,  its  simple  alimentary  canal,  and  its  mode  of  attach- 
ment to  foreign  bodies,  it  has  a  greater  affinity  to  the  latter  genus.  The  modifications 
that  can  be  traced  in  the  organization  of  each  of  these  genera,  have  an  evident  re- 
ference to  the  different  situations  which  they  occupy  in  the  watery  element. 
Lingula,  living  more  commonly  near  the  surface,  and  sometimes  where  it  would  be 
'  See  Fig.  16.  - 
Y  2 
