﻿204 
  MISS 
  G. 
  L. 
  ELLES 
  OST 
  THE 
  SUBGENERA 
  [May 
  1 
  897, 
  

  

  Horizon. 
  — 
  This 
  species 
  seems 
  to 
  be 
  confined 
  to 
  the 
  zone 
  of 
  

   Monograptus 
  gregarius 
  (Lapw.). 
  It 
  is 
  most 
  abundant 
  at 
  the 
  

   horizon 
  corresponding 
  to 
  Marr 
  and 
  Nicholson's 
  zone 
  of 
  Monograptus 
  

   fimbriatus 
  (Men.), 
  in 
  the 
  Lake 
  District. 
  

  

  It 
  occurs 
  at 
  the 
  same 
  horizon 
  in 
  the 
  RastritesShales 
  of 
  Sweden 
  at 
  

   Tommarp 
  and 
  Kongslena; 
  and 
  I 
  have 
  also 
  seen 
  specimens 
  from 
  the 
  

   ' 
  colonie 
  Haidinger 
  ' 
  and 
  Berown 
  in 
  Bohemia, 
  and 
  from 
  the 
  Rastrites- 
  

   Beds 
  of 
  Bohmsdorf 
  in 
  Thuringia. 
  

  

  British 
  Localities. 
  — 
  Moffat 
  District: 
  Dobb's 
  Linn 
  (Long 
  Cliff), 
  

   Garple 
  Linn., 
  etc. 
  Lake 
  District 
  : 
  Skelgill. 
  

  

  Subgenus 
  Cephalograptus. 
  

   Cephalogeaptus 
  cometa 
  (Gein.). 
  (PI. 
  XIII. 
  figs. 
  10-16.) 
  

  

  1852. 
  Diplograpsus 
  cometa, 
  Geinitz, 
  ' 
  Die 
  Graptolithen,' 
  p. 
  26, 
  pi. 
  i. 
  fig. 
  28. 
  

  

  1853. 
  Diplograpsxis 
  cometa, 
  Richter, 
  Zeitschr. 
  d. 
  deutsch. 
  geol. 
  Gesellsch. 
  vol. 
  v. 
  

   p. 
  457, 
  pi. 
  xii. 
  figs. 
  16-17. 
  

  

  1867. 
  Diplograpsus 
  tubulariformis, 
  Nicholson, 
  Geol. 
  Mag. 
  p. 
  109, 
  pi. 
  vii. 
  fig. 
  15. 
  

  

  1868. 
  Diplograpsus 
  cometa, 
  Carruthers, 
  Geol. 
  Mag. 
  p. 
  131, 
  pi. 
  v. 
  fig. 
  4. 
  

  

  1869. 
  Cephalograptus 
  cometa, 
  Hopkinson, 
  Journ. 
  Quek. 
  Microsc. 
  Club, 
  p. 
  159, 
  

   pi. 
  viii. 
  fig. 
  14. 
  

  

  1873. 
  Cephalograptus 
  cometa, 
  Lap 
  worth, 
  Geol. 
  Mag. 
  p. 
  555 
  & 
  Proc. 
  Geol. 
  Assoc, 
  

   vol. 
  iii. 
  p. 
  167. 
  

  

  1876. 
  Cephalograptus 
  cometa, 
  Lapworth, 
  ' 
  Graptolites 
  of 
  Co. 
  Down,' 
  p. 
  132, 
  

   pi. 
  vi. 
  fig. 
  4; 
  'Cat. 
  Western 
  Scottish 
  Fossils,' 
  pi. 
  ii. 
  fig. 
  31. 
  

  

  1878-79. 
  Diplograptus 
  cometa, 
  Tornquist, 
  Geol. 
  Foren. 
  Forhandl. 
  vol. 
  iv. 
  p. 
  456. 
  

  

  1882. 
  Cephalograptus 
  cometa, 
  Tullberg, 
  K. 
  Svenska 
  Vet. 
  Akad. 
  Handl. 
  vol. 
  vi. 
  

   no. 
  13, 
  p. 
  15. 
  

  

  1890. 
  Diplograptus 
  cometa, 
  Geinitz, 
  'Graptoliten 
  des 
  k. 
  Mineralog. 
  Mus. 
  

   Dresden,' 
  pi. 
  A. 
  fig. 
  47. 
  

  

  1893. 
  Cephalograptus 
  cometa, 
  Tornquist, 
  ' 
  Structure 
  of 
  some 
  Diprionidse,' 
  K. 
  

   Fysiogr. 
  Sallsk. 
  Handl., 
  Lund, 
  vol. 
  iv. 
  p. 
  11, 
  figs. 
  36-41. 
  

  

  The 
  distinctive 
  character 
  of 
  the 
  external 
  form 
  of 
  this 
  species 
  was 
  

   recognized 
  by 
  Hopkinson 
  when 
  he 
  founded 
  the 
  subgenus 
  Cephalo- 
  

   graptus, 
  in 
  order 
  to 
  separate 
  the 
  form 
  from 
  the 
  ordinary 
  tj-pes 
  of 
  

   Diplograptus. 
  He 
  did 
  not, 
  however, 
  recognize 
  all 
  its 
  structural 
  

   characteristics. 
  It 
  was 
  left 
  to 
  Tornquist 
  to 
  do 
  this 
  in 
  his 
  work 
  on 
  

   the 
  ' 
  Structure 
  of 
  some 
  Diprionidse.' 
  Geinitz's 
  original 
  description, 
  

   and, 
  indeed, 
  all 
  the 
  earlier 
  descriptions, 
  were 
  founded 
  on 
  incomplete 
  

   specimens, 
  and 
  the 
  figures 
  given 
  are 
  therefore 
  not 
  characteristic. 
  

   In 
  his 
  more 
  recent 
  work 
  Geinitz 
  acknowledges 
  the 
  figures 
  of 
  later 
  

   authors 
  ; 
  but 
  I 
  do 
  not 
  think 
  that 
  these 
  either 
  are 
  based 
  upon 
  com- 
  

   plete 
  specimens. 
  Tornquist's 
  are 
  the 
  only 
  figures 
  on 
  which 
  reliance 
  

   may 
  be 
  placed. 
  One 
  of 
  his 
  figures 
  certainly 
  shows 
  a 
  complete 
  

   specimen, 
  and 
  he 
  alone 
  gives 
  figures 
  showing 
  the 
  characteristic 
  

   structure 
  of 
  the 
  proximal 
  end. 
  I 
  have 
  but 
  little 
  to 
  add 
  to 
  Torn- 
  

   quist's 
  work 
  in 
  this 
  respect. 
  

  

  Structure 
  of 
  the 
  Proximal 
  End. 
  — 
  As 
  Tornquist 
  has 
  shown, 
  the 
  

   sicula 
  is 
  completely 
  visible 
  in 
  both 
  obverse 
  and 
  reverse 
  positions 
  of 
  

   the 
  rhabdosoma. 
  It 
  is 
  short, 
  compared 
  with 
  the 
  great 
  length 
  

   attained 
  by 
  the 
  earliest 
  thecse. 
  It 
  is 
  about 
  T 
  L 
  inch 
  long. 
  When 
  

  

  