﻿FROM 
  THE 
  CAMBRIAN 
  STRATA 
  OF 
  NORTH 
  AMERICA, 
  ETC. 
  133 
  

  

  inner 
  wall 
  is 
  present 
  in 
  the 
  other 
  Sardinian 
  species 
  of 
  this 
  genus 
  

   described 
  by 
  Dr. 
  Bornemann. 
  

  

  The 
  septa 
  are 
  in 
  immediate 
  connexion 
  with 
  the 
  vesicular 
  

   tissues 
  of 
  the 
  outer 
  and 
  inner 
  side 
  of 
  the 
  walls. 
  Usually 
  they 
  

   are 
  distinct 
  and 
  extend 
  quite 
  across 
  tho 
  wall, 
  but 
  in 
  some 
  

   instances 
  they 
  only 
  extend 
  partially 
  across 
  and 
  curve 
  round 
  and 
  

   unite 
  together 
  (PL 
  Y. 
  figs. 
  3, 
  4). 
  They 
  are 
  apparently 
  simple, 
  thin, 
  

   cribriform 
  plates 
  ; 
  the 
  perforations 
  are 
  about 
  *2 
  millim. 
  wide 
  and 
  

   the 
  rows 
  about 
  -4 
  millim. 
  apart 
  (PI. 
  V. 
  fig. 
  5). 
  The 
  septa 
  are 
  well 
  

   developed 
  at 
  a 
  very 
  early 
  stage 
  of 
  growth 
  ; 
  in 
  sections 
  of 
  specimens 
  

   from 
  2 
  to 
  2*5 
  millim. 
  in 
  diameter 
  there 
  are 
  from 
  8 
  to 
  14 
  septa 
  ; 
  the 
  

   initial 
  number 
  in 
  another 
  specimen 
  appears 
  to 
  be 
  12. 
  The 
  number 
  

   in 
  full-grown 
  individuals 
  seems 
  to 
  be 
  in 
  proportion 
  to 
  their 
  size 
  ; 
  

   thus 
  near 
  the 
  margin 
  of 
  the 
  saucer-shaped 
  specimen 
  above 
  referred 
  

   to 
  there 
  are 
  120 
  ; 
  in 
  this 
  form 
  they 
  are 
  fairly 
  equidistant 
  from 
  each 
  

   other, 
  averaging 
  about 
  '8 
  millim. 
  apart 
  (PL 
  Y. 
  fig. 
  2). 
  

  

  The 
  arched 
  dissepiments 
  connecting 
  the 
  septa 
  laterally 
  fill 
  the 
  

   interseptal 
  loculi 
  with 
  a 
  vesicular 
  tissue. 
  In 
  some 
  cases 
  the 
  dis- 
  

   sepiments 
  show 
  small 
  cloudy 
  spots, 
  probably 
  due 
  to 
  a 
  slight 
  thick- 
  

   ening 
  of 
  their 
  substance. 
  They 
  are 
  very 
  irregularly 
  developed 
  even 
  

   in 
  the 
  same 
  specimen, 
  but 
  this 
  may 
  in 
  part 
  be 
  attributed 
  to 
  the 
  fossili- 
  

   zation. 
  They 
  are 
  not 
  present 
  in 
  the 
  Sardinian 
  specimens 
  of 
  Archa?- 
  

   ocyaihus 
  which 
  I 
  have 
  seen, 
  nor 
  are 
  they 
  mentioned 
  by 
  Bornemann 
  

   in 
  connexion 
  with 
  this 
  genus. 
  

  

  In 
  some 
  cup-shaped 
  specimens 
  the 
  wall 
  is 
  apparently 
  of 
  consider- 
  

   able 
  thickness 
  : 
  but 
  this 
  seems 
  to 
  be 
  due 
  to 
  the 
  development 
  of 
  a 
  

   successive 
  series 
  of 
  calicular 
  walls 
  one 
  within 
  the 
  other, 
  almost 
  after 
  

   the 
  manner 
  of 
  some 
  forms 
  of 
  Cyathophyllum 
  and 
  Cystiphyllum. 
  

  

  Archceocyathus, 
  as 
  defined 
  above, 
  occurs 
  in 
  the 
  Lower 
  Cambrian 
  

   strata 
  (Olenellus-zone) 
  at 
  Anse 
  au 
  Loup, 
  Labrador, 
  at 
  Troy*, 
  New 
  

   York 
  State, 
  probably 
  also 
  in 
  Nevada 
  f 
  , 
  and 
  in 
  various 
  places 
  in 
  the 
  

   south-west 
  of 
  the 
  Island 
  of 
  Sardinia, 
  whence 
  no 
  fewer 
  than 
  ten 
  

   species 
  are 
  recorded 
  by 
  Dr. 
  Bornemann 
  J. 
  

  

  Genus 
  Ethmophtllum, 
  Meek. 
  (Plate 
  Y. 
  fig. 
  7.) 
  

  

  (1868. 
  American 
  Journal 
  of 
  Science 
  and 
  Arts, 
  ser. 
  2, 
  

   vol. 
  xlv. 
  p. 
  62.) 
  

   This 
  genus 
  is 
  based 
  upon 
  specimens 
  from 
  Nevada, 
  of 
  which 
  a 
  

   preliminary 
  description, 
  without 
  figure, 
  was 
  given 
  by 
  Prof. 
  Meek, 
  

  

  * 
  The 
  Archcsocyathellus 
  ? 
  Rensselaericus, 
  Ford, 
  Am. 
  Journ. 
  Sci. 
  ser. 
  3, 
  vol. 
  v. 
  

   p. 
  211, 
  fig. 
  1, 
  is 
  not, 
  in 
  my 
  opinion, 
  generically 
  distinct 
  from 
  Archceocyathus. 
  

  

  t 
  One 
  of 
  the 
  forms 
  from 
  Nevada 
  included 
  by 
  Mr. 
  Walcott 
  in 
  Ethmophyllum 
  

   Whitneyi 
  seems 
  to 
  me, 
  judging 
  from 
  the 
  figures 
  (Bull. 
  No. 
  30, 
  pi. 
  iv. 
  fig. 
  1 
  h), 
  

   to 
  belong 
  to 
  ArchcBOcyathtts. 
  

  

  \ 
  The 
  material 
  at 
  my 
  disposal 
  is 
  insufficient 
  to 
  enable 
  me 
  to 
  discuss 
  the 
  

   characters 
  of 
  these 
  species. 
  As 
  the 
  Sardinian 
  specimens 
  are 
  all 
  imbedded 
  in 
  a 
  

   very 
  hard 
  and 
  solid 
  matrix, 
  and 
  can 
  only 
  be 
  studied 
  in 
  sections 
  which 
  it 
  is 
  ex- 
  

   tremely 
  difficult 
  to 
  orientate, 
  the 
  discrimination 
  of 
  specific 
  characters 
  is 
  

   rendered 
  very 
  complex, 
  and 
  Dr. 
  Bornemann 
  himself 
  states 
  that 
  the 
  forms 
  to 
  

   which 
  he 
  has 
  given 
  names 
  cannot 
  in 
  all 
  cases 
  strictly 
  be 
  regarded 
  as 
  definite 
  

   species. 
  Yerstein. 
  Sardiniens, 
  p. 
  50. 
  

  

  