﻿344 
  G. 
  Wi 
  SHEEESOEE 
  OX 
  THAftXISCES. 
  

  

  here 
  and 
  there. 
  Six 
  cells 
  in 
  one 
  line 
  longitudinally, 
  from 
  three 
  to 
  

   six 
  cells 
  on 
  the 
  width 
  of 
  a 
  branch. 
  

  

  The 
  habit 
  of 
  growth 
  in 
  TJiamniscas 
  is 
  characterized 
  by 
  the 
  branches 
  

   being 
  free 
  and 
  regularly 
  divided. 
  This 
  readily 
  distinguishes 
  it 
  

   from 
  any 
  associated 
  Polyzoan. 
  It 
  scarcely 
  merits 
  the 
  variable 
  cha- 
  

   racter 
  which 
  Prof. 
  King 
  gives 
  to 
  it 
  when 
  he 
  speaks 
  of 
  " 
  almost 
  every 
  

   specimen 
  offering 
  a 
  modified 
  aspect 
  "*. 
  Much 
  of 
  this 
  confusion 
  may 
  

   be 
  due 
  to 
  the 
  obscurity 
  invariably 
  present 
  in 
  the 
  Permian 
  Polyzoa, 
  

   owing 
  to 
  the 
  incrustation 
  of 
  calcic 
  carbonate 
  which 
  often 
  hides 
  their 
  

   true 
  features. 
  Owiug 
  partly 
  to 
  this 
  cause, 
  I 
  notice 
  that 
  a 
  fragment 
  

   showing 
  irregular 
  branching 
  and 
  anastomosis 
  of 
  the 
  branch 
  is 
  in- 
  

   dicated 
  as 
  an 
  instance 
  of 
  Thamniscus 
  simulating 
  the 
  character 
  of 
  

   tiynocladiaf. 
  The 
  drawing 
  in 
  question 
  is 
  clearly 
  that 
  of 
  Synocladia 
  

   and 
  not 
  Thamniscus 
  i. 
  This 
  dichotomization 
  of 
  Thamniscus 
  is 
  a 
  well- 
  

   marked 
  and 
  distinguishing 
  feature, 
  and 
  forms 
  a 
  good 
  generic 
  distinc- 
  

   tion; 
  and 
  hence, 
  in 
  redescribing 
  the 
  genus, 
  I 
  have 
  characterized 
  the 
  

   branches 
  as 
  regularly 
  instead 
  of 
  "irregularly 
  bifurcating." 
  

  

  Thamniscus 
  crassus, 
  from 
  the 
  Wenlock 
  Limestone 
  near 
  Dudley, 
  

   (From 
  drawings 
  by 
  llochfort 
  Connor, 
  Esq., 
  from 
  a 
  specimen 
  in 
  

   my 
  cabinet.) 
  

  

  A. 
  Natural 
  size. 
  B. 
  A 
  portion 
  of 
  the 
  same, 
  showing 
  the 
  cells 
  and 
  position 
  of 
  

   the 
  spiny 
  processes, 
  enlarged 
  25 
  diameters. 
  

  

  The 
  Upper 
  Silurian 
  species 
  from 
  the 
  Dudley 
  Limestone 
  I 
  propose 
  

   to 
  describe 
  as 
  

  

  Thamxisces 
  ceasses. 
  

  

  ? 
  Hornera 
  crassa, 
  Lonsd. 
  Sil. 
  Syst. 
  p. 
  077, 
  pi. 
  15. 
  figs. 
  13, 
  13 
  a. 
  

  

  ? 
  Pohjjjora 
  crassa, 
  Siluria, 
  p. 
  215, 
  Foss. 
  35 
  (i.). 
  

  

  Ceriopora, 
  Salter, 
  Cat. 
  Cambr. 
  Foss. 
  p. 
  100. 
  

  

  Hornera 
  crassa, 
  Vine, 
  Quart. 
  Jouru. 
  Geol. 
  Soc. 
  vol. 
  xxxviii. 
  p. 
  60. 
  

  

  * 
  Perm. 
  Foss. 
  England, 
  p. 
  45. 
  t 
  Ibid. 
  

  

  | 
  Ibid. 
  pi. 
  5, 
  fig. 
  10. 
  

  

  