﻿BIHANG 
  TILL 
  K. 
  SV. 
  VET.-AKAD. 
  HANDL. 
  BAND. 
  6. 
  N:0 
  13. 
  17 
  

  

  TÖUNQU., 
  Fågelsångstraktens 
  undersiluriska 
  lager; 
  Lund 
  1865, 
  p. 
  17, 
  fig. 
  

   11. 
  — 
  Did. 
  furuillatus 
  Lapworth, 
  On 
  the 
  Graptolites 
  of 
  the 
  Arenig 
  and 
  

   Llandeilo 
  Rocks 
  of 
  St 
  Davids, 
  p. 
  649. 
  ])1. 
  XXXV, 
  fig. 
  iS; 
  Quart. 
  .Tonrn. 
  

   Geol. 
  Soc, 
  1875. 
  

  

  The 
  branches 
  of 
  the 
  hydrosoma 
  grow 
  out 
  at 
  a 
  somewhat 
  

   ditFerent 
  height 
  from 
  the 
  sides 
  of 
  the 
  pointed 
  sicula; 
  the 
  

   whole 
  hydrosoma 
  attains 
  in 
  most 
  cases 
  to 
  no 
  greater 
  length 
  

   than 
  4 
  ctm.; 
  the 
  greatest 
  breadth 
  amoimts 
  to 
  3.5 
  m.m. 
  The 
  

   branches 
  are 
  rigid, 
  showing 
  underneath, 
  at 
  their 
  commencement 
  

   a 
  feeble 
  curvatiire, 
  so 
  that 
  the 
  dorsal 
  margin 
  is 
  couvex; 
  the 
  

   distal 
  part 
  is 
  straight 
  or 
  it 
  shows 
  a 
  feeble 
  curvature 
  in 
  con- 
  

   sequence 
  of 
  which 
  the 
  distal 
  points 
  of 
  the 
  branches 
  become 
  

   somewhat 
  bent 
  outwards. 
  The 
  primary 
  angle 
  of 
  the 
  branches 
  

   is 
  ordinarily 
  about 
  310°; 
  so 
  that 
  the 
  angle 
  between 
  the 
  

   branches 
  is 
  a 
  little 
  more 
  than 
  rectangular. 
  The 
  branches 
  are 
  

   commonly 
  at 
  their 
  origin 
  slender, 
  gradually 
  expanding 
  up- 
  

   wards, 
  but 
  in 
  some 
  forms 
  they 
  rapidly 
  attain 
  a 
  greater 
  

   breadth. 
  The 
  latter 
  is 
  the 
  case 
  in 
  Hisinger'8 
  type-specimen, 
  

   in 
  which 
  the 
  branches 
  narrow 
  themselves 
  verv 
  rapidly 
  to- 
  

   wards 
  the 
  base. 
  Hydrothecae 
  10 
  — 
  12 
  on 
  10 
  m.m., 
  inclined 
  

   to 
  the 
  axis 
  at 
  an 
  angle 
  of 
  about 
  45°; 
  the 
  apertural 
  margin 
  

   straight, 
  the 
  outer 
  edge 
  straight 
  or 
  somewhat 
  concave, 
  for- 
  

   ming 
  an 
  acute 
  angle 
  with 
  the 
  former; 
  apertural 
  spine 
  visible. 
  

  

  Besides 
  this 
  variety, 
  there 
  is 
  another 
  found 
  at 
  Fågel- 
  

   sång 
  which 
  seems 
  to 
  be 
  identical 
  with 
  I), 
  bifidus, 
  Hall; 
  

   but 
  it 
  occurs 
  in 
  a 
  difierent 
  horizon. 
  Forms 
  corresponding 
  to 
  

   D. 
  indentus. 
  Hall, 
  occur 
  also 
  in 
  Scania; 
  but 
  the 
  typical 
  D. 
  

   Murchisoni 
  Beck 
  (in: 
  MuRCHisoN, 
  Silurian 
  Syétem 
  1839, 
  Notes 
  

   on 
  Graptolites, 
  pag. 
  695, 
  pl. 
  24, 
  fig. 
  4), 
  which 
  is 
  characterized 
  

   by 
  its 
  considerable 
  length, 
  and 
  by 
  the 
  branches 
  showing 
  a 
  

   tendency 
  to 
  cross 
  each 
  other, 
  is 
  not 
  yet 
  found 
  in 
  Sweden. 
  

  

  Did. 
  geminus 
  occurs 
  in 
  Scania 
  at 
  Fågelsång 
  in 
  a 
  black 
  

   shale 
  underlying 
  the 
  Glossograptus- 
  and 
  Gymnogi-aj^tus-zoue; 
  

   moreover 
  it 
  is 
  found 
  in 
  Norway 
  at 
  Christiania, 
  and 
  in 
  England 
  

   in 
  the 
  lower 
  part 
  of 
  the 
  Llandeilo-group. 
  GraptoUthus 
  avus 
  

   Barr. 
  is 
  probably 
  a 
  closely 
  allied 
  species 
  to 
  that 
  under 
  de- 
  

   scription. 
  This 
  occurs 
  in 
  Barrandes 
  stratum 
  Dd 
  o. 
  

  

  No. 
  7. 
  Another 
  species 
  occurriug 
  at 
  Fågelsång 
  is 
  that 
  

   which 
  HisiNGER 
  describes 
  as 
  follows. 
  

  

  2 
  

  

  