﻿G. 
  W. 
  SHEUESOLE 
  OX 
  THAMXlSCtfS. 
  343 
  

  

  cells 
  and 
  " 
  gemmuliferous 
  vesicles." 
  The 
  supposed 
  occurrence 
  of 
  

   these 
  secondary 
  cells, 
  as 
  shown 
  by 
  King*, 
  in 
  a 
  single 
  irregular 
  line 
  

   along, 
  and 
  not 
  extending 
  across, 
  the 
  face 
  of 
  the 
  branch, 
  is 
  in 
  perfect 
  

   agreement 
  with 
  the 
  mode 
  of 
  occurrence 
  of 
  the 
  spines 
  I 
  have 
  indi- 
  

   cated. 
  

  

  Again, 
  as 
  to 
  the 
  " 
  denticle-like 
  process 
  "f 
  said 
  to 
  be 
  possessed 
  by 
  

   Thamniscus 
  dubius 
  ; 
  I 
  can 
  only 
  trace 
  this 
  to 
  the 
  unequal 
  wearing- 
  

   down 
  of 
  the 
  cell-mouth, 
  which 
  may 
  often 
  be 
  seen 
  on 
  the 
  protected 
  

   side 
  of 
  the 
  branch, 
  prominent 
  and 
  circular 
  ; 
  this 
  is 
  seen 
  to 
  weather 
  

   unequally, 
  and 
  the 
  more 
  prominent 
  portion 
  remaining 
  becomes 
  the 
  

   denticular 
  process. 
  The 
  perfect 
  cell-aperture 
  is 
  circular 
  and 
  well 
  

   defined 
  ; 
  the 
  denticular 
  process 
  is 
  therefore 
  an 
  accident, 
  and 
  not 
  a 
  

   natural 
  occurrence. 
  

  

  These 
  details 
  are 
  necessary 
  to 
  justify 
  the 
  course 
  which 
  I 
  intend 
  

   to 
  take 
  ; 
  for 
  with 
  the 
  discovery 
  of 
  Carboniferous 
  and 
  Silurian 
  Tham- 
  

   niscidaa, 
  it 
  is 
  obvious 
  that 
  if 
  King's 
  diagnosis 
  of 
  the 
  genus 
  is 
  correct, 
  

   then 
  a 
  new 
  genus 
  would 
  be 
  necessary 
  to 
  receive 
  them. 
  Happily 
  it 
  

   has 
  been 
  shown 
  that 
  this 
  addition 
  is 
  not 
  needful. 
  Take 
  away 
  the 
  

   supposed 
  cell-adjuncts 
  and 
  the 
  denticulate 
  aperture, 
  for 
  which 
  I 
  find 
  

   no 
  warrant, 
  from 
  the 
  Permian 
  species, 
  and 
  the 
  whole 
  of 
  the 
  series 
  

   are 
  in 
  perfect 
  accord. 
  

  

  Thamniscus 
  dubius 
  is 
  very 
  fully 
  described 
  and 
  figured 
  by 
  King. 
  

   As 
  to 
  the 
  drawings 
  of 
  it, 
  I 
  can 
  only 
  admit 
  fig. 
  9 
  as 
  typical 
  of 
  the 
  pori- 
  

   ferous 
  branch, 
  the 
  rest 
  are 
  misleading. 
  Fig. 
  10, 
  intended 
  for 
  Tham- 
  

   niscus, 
  really 
  represents 
  the 
  basal 
  branches 
  of 
  Synocladia 
  virgulacea 
  ; 
  

   these 
  differ 
  very 
  materially 
  in 
  appearance 
  from 
  the 
  upper 
  and 
  the 
  

   more 
  characteristic 
  portion 
  of 
  the 
  zoarium. 
  The 
  difference 
  is 
  due 
  

   to 
  a 
  thickening 
  and 
  solidifying 
  of 
  the 
  branches 
  which 
  is 
  needful 
  to 
  

   carry 
  the 
  large 
  expansion 
  of 
  Synocladia. 
  In 
  the 
  future 
  reading 
  of 
  

   the 
  genus 
  Thamniscus 
  it 
  will 
  be 
  necessary 
  to 
  omit 
  the 
  reference 
  to 
  

   " 
  gemmuliferous 
  vesicles," 
  retaining 
  as 
  its 
  distinctive 
  character 
  fre- 
  

   quent 
  and 
  regular 
  bifurcation 
  of 
  the 
  branches. 
  

  

  As 
  King's 
  generic 
  description 
  is 
  faulty 
  as 
  well, 
  it 
  will 
  be 
  neces- 
  

   sary 
  to 
  redefine 
  the 
  genus, 
  and 
  also 
  to 
  give 
  a 
  new 
  description 
  of 
  the 
  

   Permian 
  species. 
  

  

  Thamxiscus, 
  King. 
  

  

  Branches 
  free, 
  round, 
  frequently 
  and 
  regularly 
  bifurcating 
  ; 
  more 
  

   or 
  less 
  on 
  one 
  plane. 
  Zocecia 
  on 
  one 
  side. 
  Cells 
  immersed, 
  round, 
  

   arranged 
  in 
  oblique 
  lines. 
  

  

  Thamxiscus 
  dubius, 
  King. 
  

  

  /Sp. 
  char. 
  Zoarium 
  a 
  flattened 
  expansion. 
  Branches 
  free, 
  thick, 
  

   round, 
  somewhat 
  flattened, 
  frequently 
  dividing. 
  Zocecia 
  on 
  one 
  side 
  

   of 
  the 
  branch, 
  immersed 
  ; 
  apertures 
  circular 
  ; 
  peristomes 
  prominent, 
  

   about 
  their 
  own 
  diameter 
  apart, 
  arranged 
  in 
  regular 
  lines, 
  both 
  

   longitudinal 
  and 
  oblique, 
  a 
  slight 
  wavy 
  line 
  between 
  the 
  longitu- 
  

   dinal 
  rows. 
  Beverse 
  finely 
  striate, 
  Bemains 
  of 
  spiniferous 
  processes 
  

  

  * 
  Perm. 
  Foss. 
  England, 
  pi. 
  v. 
  fig. 
  lib. 
  

   t 
  Ibid. 
  pi. 
  v. 
  fig. 
  12. 
  

  

  2a2 
  

  

  