ME.  HAJfCOCK  ON  THE  OEGANIZATION  OF  THE  BEACHIOPODA. 
85.1 
mantle  carefully  examined,  that  its  distinctive  character  was  observ'ed.  It  is,  however, 
smaller,  considerably  narrower  in  proportion  to  its  length,  and  has  the  shell  of  a brighter 
green  colour  than  the  species  with  which  it  was  associated;  but  the  most  important 
character  is  found  in  connexion  with  the  pallial  lobes,  in  which  the  pallial  sinuses  do 
not  assume  the  form  of  gill-like  plicee  arranged  in  parallel  order ; on  the  contrary,  they 
are  much  branched  (Plate  LXVI.  figs.  1 and  2),  resembling  the  pseudo-vascular  ramifi- 
cations of  some  of  the  articulated  Brachiopods, 
The  specimen  examined  was  2 inches  long  and  f ths  of  an  inch  broad. 
No.  2. — -The  valves  of  the  Brachiopods  are  undoubtedly  related  anatomically,  as  stated 
in  the  text,  though  perhaps  they  ought  both  to  be  considered  dorsal  as  well  as  those  of 
the  Lamellibranchs,  as  has  been  pointed  out  by  Professor  Huxley.  If  this  view  be  cor- 
rect, the  only  difierence  in  the  arrangement  of  the  valves  of  the  two  classes  will  be  that, 
while  in  the  latter  they  are  united  along  the  dorsal  ridge,  they  are  articulated  across  the 
back  in  the  Brachiopods. 
No.  3. — Dr.  Vogt,  in  his  well-known  paper  ‘On  the  Anatomy  oi  Lingula  anatina,' 
preHously  quoted  in  the  text,  has  given  a minute,  though  erroneous  description  of  the 
so-called  gill-organ,  ha\ing  apparently  entirely  misunderstood  the  anatomy  of  the  part. 
He  has  certainly  failed  to  recognize  the  true  nature  of  the  great  pallial  sinuses,  is  not 
aware  that  they  communicate  with  the  perivisceral  chamber,  and  what  he  describes  as 
the  vascular  ramifications  of  the  “gill-leaf”  are  not  vessels  at  all;  the  “gill-leaf”  itself 
is  a portion  of  the  inner  palhal  lamina,  and  the  “cilia-leaf”  is  the  remainder  of  the 
mantle,  being  chiefiy  composed  of  the  outer  lamina. 
In  both  the  species  of  Lingula  that  I have  examined  there  is  a white  line  running 
along  the  outer  wall  of  the  pallial  sinuses  (Plates  LXIV.  figs.  I and  2 d ; LXVI.  fig.  I c,  e), 
which,  upon  a cursory  inspection,  might  be  erroneously  supposed  to  be  of  the  nature  of 
a similar  line  which  is  observed  in  the  articulated  Brachiopods,  and  which  in  them  is 
produced  by  the  base  of  the  membrane  suspending  the  genitalia.  In  Lingula^  however, 
this  line  is,  as  just  stated,  in  connexion  with  the  outer  pallial  lamina,  while  in  the  arti- 
culated Brachiopods  it  is  connected  with  the  inner  lamina.  And  moreover  these  lines 
in  the  central  and  lateral  sinuses  of  the  latter  are  united  to  that  of  the  trunk-sinus,  but 
they  are  not  so  united  in  Lingula ; those  of  the  lateral  branches  in  it  reach  no  further 
than  the  margins  of  the  trunk-sinus,  a considerable  space  being  left  between  their  ter- 
minations and  the  line  in  that  sinus.  This  fact  is  conclusive  against  these  lines  being 
vascular  ramifications,  and  yet  it  would  seem  that  they  are  the  vessels  of  the  “ gill-leaf,” 
according  to  Dr.  Vogt,  for  there  is  nothing  else  to  be  found  in  connexion  with  the 
mantle  that  at  all  answers  to  his  description,  which  is  sufficiently  accurate  on  this  point. 
These  vascular  ramifications  are,  says  this  eminent  anatomist,  “ surrounded  by  a trans- 
lucent space,  which  is  produced  by  a hollow  canal  in  which  the  vessels  lie.”  This  is 
exactly  the  appearance  the  white  lines  assume  in  relation  to  the  pallial  sinuses  when 
