﻿FROM 
  THE 
  LOWER 
  SILURIAN 
  OE 
  NORTH 
  AMERICA. 
  

  

  509 
  

  

  sized 
  corallites, 
  are 
  entirely 
  occupied 
  by 
  very 
  minute 
  tubuli 
  similar 
  

   to 
  those 
  which 
  separate 
  the 
  ordinary 
  calices. 
  

  

  Some 
  of 
  the 
  thinner 
  examples 
  included 
  under 
  this 
  head 
  have 
  a 
  

   resemblance 
  to 
  Monticulipora 
  pavonia, 
  D'Orbigny 
  ; 
  but 
  their 
  charac- 
  

   ters 
  appear 
  to 
  be 
  quite 
  different. 
  

  

  Locality 
  and 
  Formation. 
  Common 
  in 
  the 
  Cincinnati 
  group, 
  near 
  

   Cincinnati, 
  Ohio. 
  Collected 
  by 
  Prof. 
  Edward 
  Orton 
  and 
  Mr. 
  TJ. 
  P. 
  

   James. 
  

  

  14. 
  Ch^tetes 
  ? 
  clathratijltjs, 
  James. 
  PI. 
  XXX. 
  figs. 
  1-1 
  b. 
  

  

  Stictopora 
  clathratula, 
  James, 
  Catalogue 
  of 
  the 
  Fossils 
  of 
  the 
  Cin- 
  

   cinnati 
  Group, 
  1871 
  (named, 
  but 
  not 
  figured 
  or 
  described). 
  

  

  Corallum 
  forming 
  a 
  thin 
  undulating 
  expansion 
  of 
  considerable 
  

   size, 
  and 
  about 
  half 
  a 
  line, 
  less 
  or 
  more, 
  in 
  thickness. 
  The 
  corallum 
  

   evidentlv 
  grew 
  in 
  an 
  erect 
  position, 
  as 
  it 
  consists 
  of 
  two 
  layers 
  of 
  

   corallites, 
  which 
  have 
  their 
  bases 
  fixed 
  to 
  a 
  common 
  membrane, 
  and 
  

   open 
  on 
  opposite 
  sides 
  of 
  the 
  corallum. 
  The 
  corallites 
  are 
  thus 
  

   about 
  one 
  quarter 
  of 
  a 
  line 
  in 
  height, 
  and 
  they 
  are 
  slightly 
  oblique 
  

   to 
  the 
  central 
  lamina 
  and 
  also 
  to 
  the 
  surface 
  on 
  which 
  they 
  open. 
  

   The 
  calices 
  are 
  somewhat 
  oblique, 
  the 
  lower 
  lip 
  very 
  slightly 
  promi- 
  

   nent, 
  the 
  walls 
  moderately 
  thick. 
  About 
  ten 
  of 
  the 
  calices 
  occupy 
  

   the 
  space 
  of 
  one 
  line, 
  their 
  size 
  being 
  nearly 
  equal 
  throughout 
  and 
  

   their 
  general 
  form 
  being 
  oval. 
  The 
  calices 
  are 
  arranged 
  in 
  regularly 
  

   decussating 
  diagonal 
  lines, 
  which 
  cross 
  the 
  corallum 
  from 
  side 
  to 
  

   side 
  in 
  two 
  intersecting 
  directions. 
  Surface 
  with 
  low, 
  rounded, 
  

   obscure 
  elevations, 
  arranged 
  in 
  diagonal 
  rows 
  at 
  intervals 
  of 
  from 
  

   one 
  line 
  to 
  a 
  line 
  and 
  a 
  half, 
  and 
  occupied 
  by 
  cells 
  which, 
  as 
  a 
  rule, 
  

   are 
  neither 
  larger 
  nor 
  smaller 
  than 
  the 
  average. 
  The 
  ordinary 
  

   corallites 
  never 
  have 
  minute 
  tubes 
  interspersed 
  amongst 
  them 
  ; 
  but 
  

   there 
  are 
  often 
  some 
  small 
  corallites 
  on 
  the 
  elevations. 
  

  

  This 
  beautiful 
  fossil 
  might 
  be 
  taken 
  at 
  first 
  sight 
  for 
  a 
  Ptilodictya, 
  

   though 
  it 
  appears 
  to 
  be 
  clearly 
  not 
  of 
  this 
  nature. 
  I 
  have, 
  how- 
  

   ever, 
  been 
  unable 
  to 
  make 
  out 
  the 
  presence 
  of 
  tabulae, 
  and 
  am 
  

   therefore 
  uncertain 
  what 
  its 
  true 
  affinities 
  may 
  be. 
  In 
  the 
  

   form 
  of 
  the 
  calices. 
  in 
  its 
  mode 
  of 
  growth, 
  and 
  in 
  the 
  presence 
  ot 
  

   low 
  tubercles 
  more 
  especially, 
  it 
  resembles 
  a 
  Chcetetes, 
  and 
  I 
  have 
  

   provisionally 
  referred 
  it 
  to 
  this 
  genus. 
  The 
  largest 
  specimen 
  m 
  my 
  

   possession 
  is 
  an 
  undulated 
  expansion, 
  broken 
  on 
  all 
  sides 
  about 
  

   3 
  inches 
  long 
  by 
  2i 
  inches 
  wide, 
  and 
  about 
  | 
  a 
  line 
  thick 
  My 
  

   description 
  is 
  drawn 
  from 
  type 
  specimens 
  presented 
  to 
  me 
  by 
  Mr. 
  

  

  ~P 
  TflTTlPfl 
  

  

  'Locality 
  and 
  Formation. 
  Cincinnati 
  group, 
  near 
  Cincinnati, 
  

   Ohio. 
  

  

  III. 
  Massive 
  and 
  Discoid 
  Species. 
  

   Corallum 
  fixed 
  or 
  free, 
  massive, 
  discoidal, 
  hemispherical, 
  spheri- 
  

   cal, 
  or 
  irregular 
  in 
  shape. 
  The 
  typical 
  forms 
  of 
  this 
  group 
  have 
  the 
  

   under 
  surface 
  of 
  the 
  corallum 
  covered 
  by 
  an 
  epitheca 
  ; 
  and 
  these 
  

   must 
  have 
  had 
  a 
  free 
  existence, 
  as 
  the 
  under 
  surface 
  of 
  the 
  coral- 
  

  

  