﻿138 
  DR. 
  G. 
  J. 
  HTNDE 
  ON 
  ARCH^OCYATHUS 
  AND 
  OTHER 
  GENERA 
  

  

  sition 
  of 
  numerous 
  secondary 
  layers 
  on 
  its 
  inner 
  side. 
  Owing 
  to 
  

   the 
  infilling 
  of 
  the 
  axial 
  tube 
  by 
  the 
  solid 
  matrix, 
  the 
  characters 
  of 
  

   the 
  inner 
  surface 
  of 
  the 
  wall 
  can 
  only 
  be 
  seen 
  in 
  the 
  sections 
  ; 
  it 
  

   appears 
  to 
  be 
  uneven, 
  with 
  projecting 
  points 
  and 
  ridges, 
  and 
  to 
  be 
  

   penetrated 
  by 
  wide 
  canals. 
  

  

  In 
  one 
  portion 
  of 
  the 
  central 
  tube 
  of 
  the 
  type 
  specimen 
  a 
  section 
  

   of 
  a 
  small 
  individual, 
  2 
  millim. 
  in 
  diameter 
  *, 
  is 
  exposed, 
  which 
  

   may 
  be 
  of 
  the 
  nature 
  of 
  a 
  bud, 
  though 
  its 
  connexion 
  with 
  the 
  

   larger 
  specimen 
  is 
  not 
  definitely 
  shown. 
  

  

  The 
  character 
  and 
  arrangement 
  of 
  the 
  structures 
  in 
  the 
  wall 
  of 
  

   Spirocyaihus 
  definitely 
  mark 
  it 
  off 
  from 
  Archceocyathus 
  and 
  the 
  

   allied 
  genera 
  in 
  which 
  there 
  are 
  distinct 
  radial 
  vertical 
  septa. 
  In 
  

   general 
  charactersf 
  Spirocyaihus 
  approaches 
  Protopharetra, 
  Bornem., 
  

   the 
  principal 
  differences 
  being 
  the 
  peculiar 
  primary 
  and 
  secondary 
  

   layers 
  in 
  the 
  wall-plates 
  and 
  the 
  absence 
  of 
  tabulae 
  (Boderi) 
  ; 
  

   further 
  it 
  is 
  a 
  simple 
  form. 
  

  

  The 
  only 
  species 
  at 
  present 
  known 
  is 
  Spirocyaihus 
  atlanticus, 
  

   Bill., 
  sp., 
  from 
  the 
  lowest 
  fossiliferous 
  or 
  Olenellus-zone 
  of 
  the 
  

   Cambrian 
  at 
  Anse 
  au 
  Loup, 
  Labrador. 
  It 
  is 
  also 
  present 
  at 
  the 
  

   corresponding 
  horizon 
  in 
  Nevada, 
  as 
  shown 
  by 
  Air. 
  Walcott 
  £. 
  

  

  4. 
  Affinities 
  of 
  Archseocyathus 
  and 
  allied 
  forms. 
  

  

  The 
  genera 
  Archceocyathus, 
  Bill., 
  Coscinocyaihus, 
  Bornem., 
  An- 
  

   iliomorpha, 
  Bornem., 
  and 
  the 
  provisional 
  genus 
  Protopharetra, 
  

   Bornem., 
  were 
  included 
  by 
  Dr. 
  Bornemann 
  § 
  as 
  a 
  separate 
  group 
  of 
  

   the 
  Ccelenterata 
  under 
  the 
  name 
  of 
  the 
  Archa30cyathinge. 
  In 
  the 
  

   same 
  group 
  may 
  now 
  be 
  reckoned 
  Ethmophyllum, 
  Meek, 
  and 
  Spirocya- 
  

   tlius, 
  gen. 
  no 
  v. 
  Of 
  these 
  genera, 
  Protopharetra 
  and 
  Spirocyaihus 
  are 
  

   closely 
  related 
  together, 
  and 
  differ 
  from 
  the 
  others 
  in 
  the 
  absence 
  of 
  

   distinct 
  radial 
  septa 
  and 
  some 
  other 
  features 
  ; 
  but 
  in 
  their 
  minute 
  

   structure 
  and 
  their 
  general 
  plan 
  of 
  growth 
  they 
  are 
  similar, 
  and 
  may 
  

   be 
  regarded 
  as 
  belonging 
  to 
  the 
  same 
  group, 
  the 
  zoological 
  relations 
  

   of 
  which 
  we 
  now 
  propose 
  to 
  consider. 
  

  

  First, 
  as 
  regards 
  their 
  relationship 
  to 
  Sponges, 
  with 
  which 
  they 
  

  

  * 
  Mr. 
  Walcott 
  seems 
  to 
  have 
  been 
  the 
  first 
  to 
  call 
  attention 
  to 
  this 
  young 
  

   specimen. 
  See 
  Bull. 
  no. 
  30, 
  p. 
  73. 
  

  

  t 
  I 
  have 
  felt 
  considerable 
  difficulty 
  in 
  determining 
  whether 
  Spirocyathus 
  

   could 
  be 
  established 
  as 
  a 
  genus 
  distinct 
  from 
  Protopharetra, 
  Bornem. 
  ; 
  for 
  

   though 
  I 
  hare 
  not 
  seen 
  in 
  the 
  specimens 
  sent 
  me 
  from 
  Sardinia 
  the 
  peculiar 
  

   characters 
  of 
  the 
  Trail-plates 
  so 
  conspicuous 
  in 
  the 
  former 
  genus, 
  it 
  is 
  just 
  

   possible 
  that 
  these 
  features 
  might 
  hare 
  been 
  lost 
  in 
  the 
  fossilization 
  of 
  the 
  

   Sardinian 
  forms 
  of 
  Protopharetra. 
  I 
  hare 
  also 
  felt 
  the 
  further 
  objection 
  to 
  

   merging 
  Spirocyaihus 
  atlanticus 
  under 
  Protopharetra, 
  since 
  Dr. 
  Bornemann 
  has 
  

   expressly 
  stated 
  (Verstein. 
  Sardiniens, 
  pp. 
  47, 
  48) 
  that 
  this 
  latter 
  does 
  not 
  

   indicate 
  an 
  independent 
  genus 
  ; 
  whereas, 
  whatever 
  may 
  be 
  the 
  case 
  with 
  the 
  

   Sardinian 
  forms, 
  I 
  can 
  entertain 
  no 
  doubt 
  that 
  the 
  type 
  of 
  Spirocyaihus 
  is 
  of 
  

   itself 
  quite 
  independent 
  of 
  Archaocyathus. 
  

  

  \ 
  Bull. 
  no. 
  30, 
  pi. 
  iii. 
  figs. 
  1 
  b, 
  2, 
  2 
  a. 
  

  

  § 
  Zeitschr. 
  d. 
  deutsch. 
  geol. 
  Gesellsch. 
  1884, 
  p. 
  706 
  ; 
  Versteinerungen 
  Sar 
  

   diniens, 
  p. 
  28. 
  

  

  