﻿816 
  Forty-seventh 
  Report 
  on 
  tee 
  State 
  Museum. 
  

  

  These 
  manifest 
  themselves 
  only 
  in 
  later 
  or 
  post-larval 
  growth- 
  

   stages, 
  and 
  as 
  they 
  are 
  a 
  product 
  of 
  the 
  mantle 
  lobes, 
  may 
  par- 
  

   take 
  of 
  the 
  same 
  punctate 
  structure 
  as 
  the 
  valves. 
  

   ^These 
  plates 
  may 
  unite 
  along 
  the 
  median 
  line, 
  obliterate 
  the 
  

   foramen, 
  or 
  even 
  extinguish 
  all 
  trace 
  of 
  their 
  original 
  division, 
  as 
  

   frequently 
  seen 
  in 
  Spieifek, 
  Cyrtia 
  and 
  Cyrtina 
  (pseudodel- 
  

   tidium), 
  thus 
  simulating 
  in 
  every 
  respect 
  the 
  true 
  deltidium 
  ; 
  

   though 
  it 
  is 
  now 
  evident 
  that 
  these 
  and 
  the 
  deltidium 
  are 
  of 
  

   fundamentally 
  different 
  nature. 
  These 
  structures, 
  then, 
  become 
  

   at 
  once 
  a 
  most 
  important 
  basis 
  of 
  classification 
  among 
  the 
  articu- 
  

   late 
  Brachiopods. 
  

  

  In 
  this 
  work 
  the 
  term 
  spondylium 
  has 
  been 
  applied 
  to 
  the 
  spoon 
  

   shaped 
  plate 
  which, 
  when 
  present, 
  is 
  usually 
  found 
  in 
  the 
  pedicle- 
  

   valve 
  only, 
  but 
  among 
  the 
  pentameroids 
  frequently 
  occurs 
  in 
  

   both 
  valves. 
  It 
  has 
  become 
  evident 
  since 
  the 
  introduction 
  of 
  the 
  

   term 
  that 
  these 
  processes 
  in 
  the 
  two 
  valves, 
  though 
  similar 
  in 
  

   aspect, 
  are 
  similar 
  neither 
  in 
  origin 
  nor 
  junction, 
  and 
  it 
  becomes 
  

   necessary 
  to 
  modify 
  the 
  application 
  of 
  this 
  term. 
  Hence 
  it 
  is 
  

   proposed 
  to 
  restrict 
  the 
  term 
  spondylium 
  to 
  the 
  plate 
  existing 
  in 
  

   the 
  pedicle-valve, 
  and 
  to 
  the 
  plates 
  of 
  the 
  brachial 
  valve, 
  whether 
  

   united 
  or 
  discrete, 
  the 
  name 
  cruralium 
  will 
  be 
  applied. 
  The 
  

   distinction 
  of 
  the 
  parts 
  is 
  necessary 
  to 
  a 
  proper 
  apprehension 
  of 
  

   their 
  value. 
  

  

  The 
  spondylium 
  is 
  an 
  area 
  of 
  muscular 
  implantation. 
  In 
  its 
  

   early 
  or 
  incipient 
  condition 
  it 
  is 
  evident 
  that 
  it 
  originates 
  from 
  

   the 
  convergence 
  and 
  coalescence 
  of 
  the 
  dental 
  lamellse, 
  and 
  forms 
  

   a 
  receptacle 
  for 
  the 
  proximal 
  portion 
  of 
  the 
  pedicle, 
  and 
  for 
  the 
  

   capsular 
  or 
  pedicle 
  muscles. 
  In 
  CnrAMBONiTEs 
  and 
  Pentamercs, 
  

   where 
  it 
  attains 
  its 
  greatest 
  development, 
  it 
  bears 
  all 
  the 
  muscles 
  

   of 
  the 
  valve, 
  the 
  central 
  adductor, 
  and 
  the 
  lateral 
  diductor 
  scars 
  

   being 
  often 
  clearly 
  defined, 
  while 
  the 
  posterior 
  portion 
  of 
  the 
  plate 
  

   is 
  still 
  reserved 
  for 
  the 
  attachment 
  of 
  the 
  pedicle, 
  if 
  functional. 
  

   Considering 
  this 
  structure 
  in 
  its 
  incipient 
  condition, 
  where, 
  as 
  in 
  

   Orthis, 
  it 
  is 
  represented 
  only 
  by 
  the 
  convergent 
  dental 
  plates 
  

   which 
  usually 
  unite 
  with, 
  or 
  rest 
  upon 
  the 
  bottom 
  of 
  the 
  valve 
  

   and 
  enclose 
  only 
  the 
  base 
  of 
  the 
  pedicle 
  and 
  its 
  muscles, 
  it 
  will 
  

   be 
  evident 
  that 
  the 
  plate 
  is 
  actually 
  but 
  a 
  modification 
  of 
  the 
  

   original 
  pedicle-sheath. 
  It 
  is, 
  evidently, 
  the 
  inner 
  moiety 
  of 
  this 
  

   sheath 
  surrounding 
  the 
  pedicle, 
  which 
  has 
  become 
  involved 
  or 
  

  

  