﻿Vol. 
  53-1 
  

  

  PETALOGRAPTTJS 
  AND 
  CEPHALOGRAPTUS. 
  

  

  199 
  

  

  Table 
  of 
  Measurements 
  of 
  different 
  Varieties 
  of 
  

   P. 
  palmees 
  (Ban.). 
  

  

  No. 
  

  

  Species. 
  

  

  Lngth. 
  

  

  L. 
  of 
  

  

  sicula. 
  

  

  W. 
  opp. 
  

   ap. 
  I 
  1 
  . 
  

  

  Max. 
  

   width. 
  

  

  Thecal 
  

  

  length. 
  

  

  •No. 
  of 
  

   thecas. 
  

  

  No. 
  to 
  

   inch. 
  

  

  Locality. 
  

  

  a. 
  

  

  P. 
  palmeus... 
  

  

  3 
  

  

  

  

  tV 
  

  

  ~tV 
  

  

  

  32 
  

  

  Conway. 
  

  

  l 
  b 
  . 
  

  

  P. 
  palmeus... 
  

  

  5 
  

  

  -iV 
  

  

  A 
  

  

  T2~ 
  

  

  tV 
  

  

  

  

  Zelkovice. 
  

  

  2. 
  

  

  var. 
  tenuis 
  ... 
  

  

  t\ 
  

  

  

  A 
  

  

  1 
  

  

  TS" 
  

  

  1 
  

   33 
  

  

  13 
  

  

  36 
  

  

  Belcraig. 
  

  

  3. 
  

  

  var. 
  tenuis 
  ... 
  

  

  s 
  

  

  1 
  

  

  A 
  

  

  TT 
  

  

  1 
  

  

  ■2* 
  

  

  11 
  

  

  36 
  [ 
  

  

  Dobb's 
  

  

  Linn. 
  

  

  6°. 
  

  

  var. 
  latus 
  ... 
  

  

  3" 
  

  

  

  A 
  

  

  * 
  

  

  + 
  tV 
  

  

  26 
  

  

  36 
  

  

  » 
  

  

  10. 
  

  

  var. 
  latus 
  ... 
  

  

  + 
  ^ 
  

  

  -^ 
  

  

  i 
  

  

  1 
  

   ■g 
  

  

  + 
  A 
  

  

  23 
  

  

  36 
  

  

  » 
  

  

  9. 
  

  

  var. 
  oua^o-1 
  

   elongatus 
  j 
  

  

  ? 
  

  

  1 
  

  

  tV 
  

  

  * 
  

  

  +A 
  

  

  26 
  

  

  36 
  

  

  - 
  

  

  36. 
  

  

  Tar. 
  orafo-1 
  

   elongatus 
  J 
  

  

  + 
  1 
  

  

  1 
  

  

  i 
  2 
  

  

  T2 
  

  

  1 
  

   6 
  

  

  +tV 
  

  

  

  

  Skelgill. 
  

  

  Petalograptus 
  oyatus 
  (Barr.). 
  (PI. 
  XIV. 
  figs. 
  15-16.) 
  

  

  1850. 
  Grraptolithus 
  ovatus, 
  Barrande, 
  ' 
  Grapt. 
  de 
  Boheme,' 
  i. 
  p. 
  63, 
  pi. 
  iii. 
  figs. 
  8, 
  9. 
  

  

  1851. 
  Petalolithus 
  ovatus, 
  Suss, 
  ' 
  Ueber 
  Bohmische 
  Grapt.' 
  p. 
  21, 
  pi. 
  viii. 
  fig. 
  3. 
  

  

  1852. 
  Diplograpsus 
  ovatus, 
  Geinitz, 
  ' 
  Die 
  Graptolithen,' 
  p. 
  20, 
  pi. 
  i. 
  figs. 
  3 
  & 
  4. 
  

   1890. 
  Diplograptus 
  ovatus, 
  Geinitz, 
  ' 
  Graptoliten 
  des 
  k. 
  Mineralog. 
  Mus. 
  Dresden,' 
  

  

  p. 
  25, 
  pi. 
  A. 
  fig. 
  37. 
  

  

  With 
  the 
  exception 
  of 
  one 
  very 
  doubtful 
  form 
  from 
  the 
  Tarannon 
  

   Shales 
  of 
  Conway, 
  North 
  Wales, 
  I 
  have 
  never 
  seen 
  a 
  British 
  specimen 
  

   that 
  conld 
  correctly 
  be 
  referred 
  to 
  P. 
  ovatus 
  (Barr.). 
  As 
  far 
  as 
  our 
  

   present 
  knowledge 
  goes, 
  the 
  typical 
  form 
  at 
  any 
  rate 
  does 
  not 
  seem 
  

   to 
  have 
  been 
  recognized 
  outside 
  Bohemia. 
  

  

  The 
  species 
  is 
  exceedingly 
  characteristic, 
  and 
  can 
  readily 
  be 
  dis- 
  

   tinguished 
  from 
  all 
  other 
  forms 
  ; 
  but, 
  in 
  spite 
  of 
  this, 
  many 
  young 
  

   forms 
  of 
  other 
  species 
  have 
  been 
  erroneously 
  referred 
  to 
  it. 
  The 
  

   specimens 
  from 
  Bohemia 
  in 
  the 
  British 
  Museum 
  (Natural 
  History) 
  

   have 
  had 
  for 
  some 
  unaccountable 
  reason 
  Barrande's 
  original 
  labels 
  

   corrected, 
  and 
  now 
  bear 
  the 
  name 
  D. 
  folium 
  (His.), 
  though 
  they 
  are 
  

   typical 
  forms 
  of 
  P. 
  ovatus 
  (Barr.), 
  and 
  bear 
  little 
  or 
  no 
  resemblance 
  

   to 
  Hisinger's 
  species. 
  

  

  Structure 
  of 
  the 
  Proximal 
  End. 
  — 
  The 
  sicula 
  has 
  a 
  peculiar 
  

   shape 
  ; 
  it 
  is 
  broad, 
  curved, 
  and 
  about 
  y 
  L 
  inch 
  long. 
  It 
  reaches 
  up 
  

   to 
  the 
  third 
  theca 
  of 
  each 
  series, 
  and 
  is 
  furnished 
  with 
  a 
  short 
  

   apertural 
  spine. 
  The 
  earliest 
  thecae 
  are 
  both 
  very 
  curved 
  ; 
  the 
  first 
  

   of 
  the 
  primordial 
  series 
  arises 
  near 
  the 
  base 
  of 
  the 
  sicula, 
  and 
  is 
  so 
  

   much 
  curved 
  that 
  the 
  aperture 
  is 
  almost 
  on 
  a 
  level 
  with 
  the 
  point 
  at 
  

   which 
  the 
  ' 
  primordial 
  bud 
  ' 
  arose. 
  The 
  second 
  theca 
  (l 
  2 
  ) 
  is 
  very 
  

   nearly 
  as 
  much 
  curved. 
  Sometimes 
  these 
  two 
  earliest 
  thecae 
  are 
  

   very 
  short, 
  at 
  others 
  they 
  do 
  not 
  differ 
  greatly 
  in 
  length 
  from 
  those 
  

   thecae 
  which 
  arise 
  later. 
  

  

  