﻿12 
  S. 
  A. 
  TULLBERG, 
  GRAPTOLITfiS 
  DESCRIBED 
  BY 
  HISINGER. 
  

  

  the 
  same, 
  as 
  that 
  which 
  Lapwoeth 
  has 
  named 
  Monograptus 
  

   leptotheca. 
  Yet 
  it 
  appears 
  from 
  other 
  species 
  in 
  Hisingek's 
  

   collectioD, 
  which 
  also 
  are 
  labelled 
  Pr. 
  sagittarius, 
  that 
  Hi- 
  

   SINGER 
  himself 
  used 
  this 
  namo 
  for 
  all 
  straight 
  Monograpti, 
  

   aud 
  also 
  for 
  fragments 
  of 
  the 
  branches 
  of 
  the 
  Dichograptidae. 
  

   The 
  form, 
  which 
  Lä.pwoeth 
  names 
  M. 
  leptotheca, 
  occurs 
  

   in 
  Sweden 
  alwavs 
  in 
  company 
  with 
  M. 
  convolutus, 
  M. 
  lohifer, 
  

   JJipl. 
  foliuiu 
  and 
  Climacograptus 
  scalaris; 
  that 
  is 
  in 
  other 
  

   words 
  at 
  a 
  certain 
  fixed 
  horizon 
  near 
  the 
  base 
  of 
  the 
  upper 
  

   graptolite-bearing 
  shales. 
  And 
  it 
  is 
  just 
  from 
  this 
  stage 
  that 
  

   HisiNGER 
  and 
  Wahlenberg 
  collected 
  several 
  of 
  their 
  grap- 
  

   tolites. 
  As 
  in 
  this 
  zone 
  bo 
  other 
  Monograptus 
  is 
  found, 
  which 
  

   could 
  have 
  been 
  meant 
  by 
  the 
  name 
  »sagittarius-» 
  (for 
  the 
  

   zone 
  with 
  M. 
  cyplius, 
  the 
  only 
  species 
  that 
  might 
  be 
  suggested 
  

   is 
  not 
  found 
  represented 
  in 
  Vcstrogothia), 
  I 
  take 
  it 
  we 
  are 
  

   warranted 
  in 
  assuming 
  that 
  Wahlenberg 
  also 
  by 
  the 
  name 
  of 
  

   »sagittarius» 
  has 
  meant 
  this 
  species. 
  He 
  considers 
  it 
  provisionally 
  

   as 
  the 
  moiety 
  of 
  an 
  Orthoceratites 
  tenuis 
  produced 
  by 
  splitting. 
  

   Although 
  Linné, 
  by 
  naming 
  it 
  Graptolithus 
  sagittarius, 
  by 
  

   that 
  name 
  signified 
  all 
  the 
  Monograpti 
  with 
  sawlike 
  teeth, 
  it 
  is 
  

   however 
  probable, 
  that 
  his 
  material 
  was 
  not 
  rich 
  and 
  that 
  the 
  

   name 
  could 
  be 
  fixed 
  on 
  a 
  certain 
  species 
  in 
  the 
  modern 
  sense. 
  

  

  Monograptus 
  leptotheca. 
  Lapw. 
  

  

  Plate 
  II, 
  fig. 
  8-12. 
  

  

  Grajjtolitlii 
  sagittarli 
  Linnaei 
  apud 
  Wahlenberg 
  Petr. 
  Svec. 
  p. 
  93. 
  

   — 
  Prlonotus 
  sagittarius 
  His. 
  1. 
  c. 
  — 
  Monogr. 
  leptotheca 
  Lapworth. 
  On 
  

   ScottJsh 
  Monograptidse, 
  Geol. 
  Mag., 
  Dec. 
  II, 
  vol. 
  III, 
  1876 
  Pl. 
  XII, 
  fig. 
  4. 
  

  

  The 
  hydrosoma 
  is 
  about 
  15 
  ctm. 
  long, 
  almost 
  straight 
  or 
  

   a 
  little 
  bent, 
  the 
  proximal 
  part 
  long, 
  narrow, 
  iucreasing 
  in 
  

   breadth 
  by 
  degrees, 
  which 
  at 
  last 
  amounts 
  to 
  2,5—3 
  mm. 
  on 
  

   the 
  fuUy 
  developed 
  part. 
  The 
  general 
  form 
  of 
  the 
  hydrosoma 
  

   is 
  straight, 
  but 
  the 
  first 
  formed 
  hydrothecae 
  are 
  placed 
  on 
  the 
  

   convex 
  margin, 
  whereas 
  the 
  ventral 
  margin 
  sometimes 
  is 
  con- 
  

   cave 
  on 
  the 
  distal 
  part. 
  The 
  hydrothecae 
  consist 
  of 
  long 
  

   and 
  narrow 
  tubes, 
  to 
  a 
  number 
  of 
  8 
  — 
  9 
  on 
  a 
  length 
  of 
  10 
  mm., 
  

   overlapping 
  each 
  other 
  to 
  a 
  great 
  extent; 
  downwards 
  they 
  are 
  

   narrow, 
  where 
  they 
  are 
  covered 
  by 
  the 
  nearest 
  inner 
  hvdro- 
  

   theca; 
  their 
  free 
  extremitv 
  swelling 
  out, 
  the 
  aperture 
  narrow: 
  

  

  