﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  177 
  

  

  Class 
  BRACHIOPODA 
  Cuvier 
  

  

  The 
  Brachiopoda 
  are 
  marine 
  animals, 
  sparingly 
  represented 
  in 
  

   modern 
  seas, 
  but 
  most 
  prolific 
  in 
  the 
  Paleozoic 
  and 
  early 
  Mesozoic 
  

   waters. 
  

  

  The 
  valves 
  of 
  the 
  brachiopod 
  shell 
  are 
  dorsal 
  and 
  ventral, 
  and 
  not 
  

   right 
  and 
  left 
  as 
  in 
  the 
  lamellibranch 
  Mollusca; 
  they 
  are 
  unequal, 
  

   and 
  each 
  is 
  symmetric 
  with 
  reference 
  to 
  a 
  median 
  line 
  (longitudinal 
  

   axis) 
  drawn 
  through 
  its 
  apex. 
  The 
  larger 
  valve 
  may 
  have 
  its 
  beak 
  

   truncated 
  or 
  furnished 
  with 
  an 
  opening 
  or 
  foramen, 
  for 
  the 
  emission 
  

   of 
  the 
  fleshy 
  pedicle, 
  by 
  means 
  of 
  which 
  the 
  animal 
  fixes 
  itself 
  to 
  

   rocks, 
  shells 
  or 
  other 
  substances. 
  

  

  Certain 
  genera, 
  such 
  as 
  Crania, 
  do 
  not 
  conform 
  to 
  this 
  mode 
  

   of 
  fixation, 
  but 
  cement 
  their 
  shell 
  directly 
  to 
  the 
  foreign 
  object, 
  

   while 
  others, 
  e.g. 
  P 
  h 
  o 
  1 
  i 
  d 
  o 
  p 
  s 
  , 
  appear 
  to 
  have 
  led 
  a 
  free 
  exist- 
  

   ence. 
  In 
  many 
  of 
  the 
  discinoid 
  genera, 
  such 
  as 
  O 
  r 
  b 
  i 
  c 
  u 
  - 
  

   1 
  o 
  i 
  d 
  e 
  a, 
  the 
  pedicle 
  passed 
  through 
  an 
  opening 
  in 
  the 
  lower 
  valve; 
  

   while 
  in 
  L 
  i 
  n 
  g 
  u 
  1 
  a 
  it 
  protruded 
  between 
  the 
  two 
  very 
  nearly 
  equal 
  

   valves. 
  In 
  all 
  cases 
  the 
  valve 
  giving 
  emission 
  to 
  the 
  pedicle 
  is 
  

   spoken 
  of 
  as 
  the 
  pedicle 
  valve. 
  

  

  The 
  opposite 
  valve 
  in 
  the 
  more 
  specialized 
  genera 
  bears 
  on 
  its 
  

   interior 
  two 
  short 
  processes, 
  or 
  crura, 
  which 
  arise 
  from 
  the 
  hinge 
  

  

  €-«. 
  

  

  Fig. 
  80 
  Diagram 
  of 
  Spirifer. 
  (AB) 
  Longitudinal 
  axis 
  marking 
  the 
  hight; 
  (CD) 
  Transverse 
  axis 
  

   marking 
  the 
  width 
  ; 
  (a» 
  Anterior 
  (front) 
  end 
  ; 
  (B) 
  posterior 
  (beak) 
  end 
  ; 
  (h) 
  hinge 
  line 
  ; 
  (ca) 
  cardina 
  

   ar 
  a; 
  (e) 
  cardinal 
  extremities; 
  (di) 
  deltidium; 
  (u) 
  umbo; 
  (a) 
  apex 
  or 
  beak 
  

  

  plate. 
  To 
  these 
  may 
  be 
  attached 
  a 
  calcareous 
  brachidium, 
  which 
  

   functions 
  as 
  a 
  support 
  for 
  the 
  delicate 
  fleshy 
  " 
  arms 
  ". 
  In 
  a 
  large 
  

   number 
  of 
  forms 
  this 
  brachidium 
  is 
  absent, 
  and 
  the 
  fleshy 
  arms 
  are 
  

   directly 
  supported 
  by 
  the 
  crura, 
  but 
  their 
  relation 
  to 
  the 
  valve 
  in 
  

   question 
  is 
  similar 
  to 
  that 
  obtaining 
  in 
  the 
  brachidium-bearing 
  

   forms. 
  This 
  valve 
  is 
  designated 
  the 
  brachial 
  valve. 
  In 
  all 
  the 
  

   forms 
  in 
  which 
  the 
  valves 
  are 
  articulated 
  with 
  each 
  other 
  

   (Brachiopoda 
  articulata) 
  such 
  articulation 
  is 
  produced 
  

   by 
  teeth 
  arising 
  from 
  the 
  pedicle 
  valve 
  and 
  lodged 
  in 
  sockets 
  in 
  the 
  

   brachial 
  valve. 
  The 
  beak 
  of 
  the 
  brachial 
  valve 
  is 
  commonly 
  fur- 
  

   nished 
  with 
  a 
  more 
  or 
  less 
  pronounced 
  cardinal 
  process, 
  which, 
  at 
  its 
  

  

  