]\IE.  HANCOCK  ON  THE  OEOANIZATION  OF  THE  BEACHIOPODA, 
829 
ing,  stiff  and  bristle-like ; they  are  marked  in  a peculiar  manner  with  transverse,  dusky 
lines,  perhaps  indicating  the  progressive  steps  of  growth. 
The  margin  of  the  mantle  has  the  same  character  in  all  the  Brachiopods,  and  in  all 
it  is  armed  with  setae,  which,  however,  vary  considerably  in  length  in  the  different  spe- 
cies. In  JV.  cranium  * the  edge  of  the  marginal  fold  is  entire,  and  the  setae  are  of  various 
lengths,  and  rather  minute  and  delicate ; rarely  more  than  two  issue  from  the  same 
follicle,  generally  only  one.  The  setae  in  T.  ca])ut-serpenUs^  are  placed  rather  far  apart 
from  each  other,  and  issue  from  the  mantle  at  the  points  corresponding  to  the  marginal 
crenrdations  of  the  shell ; these  crenulations  give  to  the  pallial  membrane  a scolloped 
appearance.  The  setae  are  rather  robust ; the  marginal  fold  is  deep,  and  the  follicles 
are  of  considerable  length  and  rather  wide,  with  their  bases  surrounded  with  glandular 
matter,  forming  a roundish,  red-coloured  spot  at  the  end  of  each  seta.  Similar  glan- 
dular matter  is  observed  at  the  bases  of  the  follicles  in  W.  australis ; but  in  that  species 
it  is  elongated  backwards.  In  R. psittacea^  the  setse  are  slender,  short  and  finely  pointed ; 
they  vary  in  length,  as  they  do  indeed  in  all  the  species,  and  occasionally  three  or  four 
issue  out  of  one  follicle.  In  all  the  species  the  setse  are  marked  with  rather  distant, 
transverse  bars.  In  Lingula'^  the  setae  are  very  long,  and  close-set,  crowding  the  marginal 
fold,  which  is  much  thickened,  and  exceedingly  deep,  forming  a mde  border  around  the 
pallial  lobe.  They  extend  entirely  round  the  dorsal  lobe,  and  in  the  ventral  one  are 
interrupted  only  for  a short  space  behind,  at  the  point  where  the  peduncle  is  attached 
to  it.  They  are  marked  with  numerous,  rather  close,  transverse  bars,  from  every  one  of 
which  a narrow  edge  projects  forward  encircling  the  setae,  giving  them  the  appearance 
of  being  jointed,  and,  as  Vogt®  observes,  rendering  them  very  like  the  stems  of  an  Equi- 
setum. 
Some  time  ago  Professor  Schmidt®  discovered  calcareous  spicula  or  plates  in  the  mantle, 
arms,  and  cirri  ofT.  capiLt-seriJentis and  more  recently  Mr.  Woodward^  exhibited,  at  a 
meeting  of  the  Zoological  Society,  not  only  spicula  in  the  pallial  lobe  of  this  species, 
but  also  in  that  of  Terehratula  mtrea  and  of  Megerlia  truncata.  This  gentleman  has 
also  found  indications  of  imbedded  calcareous  matter  in  the  mantle  of  Argiope  decollata 
and  Crania. 
In  T.  caput-serpentis^  the  spicula  are  large,  much  branched,  colourless,  glass-like  and 
pellucid,  somewhat  like  the  antlers  of  a Deer,  only  the  branches  are  all  in  the  same 
plane,  and  are  flattened  or  depressed  a little.  They  are,  however,  frequently  much  com- 
plicated, forming  a central  network,  with  irregular,  radiating  branches ; in  others,  again, 
the  branches  pass  from  a simple  perforate  centre.  These  spicula  lie  in  the  outer  layer 
of  the  inner  lamina,  and  are  crowded  to  such  a degree,  that  the  tips  of  the  branches  are 
almost  in  contact ; thus  forming  an  extensive,  though  incomplete  network  of  calcareous 
’ Plate  LIII.  figs.  3, 4.  ^ Plates  LIII.  figs.  1,  2 ; LVII.  figs.  6,  7.  ® Plate  LX.  figs.  1,  2,  3. 
^ Plates  LXIV.  figs.  1,  2 ; LVII.  figs.  8,  9.  ® Op  cit. 
' Datidsoi?',  Ann.  and  Mag.  of  Nat.  Hist.  vol.  xvi.  p.  440,  1855. 
’’  Proceedings  of  Zool.  Soc.  1856,  p.  368.  **  Plates  LII.  figs.  6,  7,  8 ; LX.  fig.  12. 
