﻿FROM 
  THE 
  LOWER 
  SILURIAN 
  OF 
  NORTH 
  AMERICA. 
  501 
  

  

  forms 
  of 
  which 
  the 
  same 
  is 
  true. 
  It 
  is, 
  however, 
  a 
  pity 
  to 
  separate 
  

   two 
  genera 
  by 
  a 
  single 
  character 
  which 
  does 
  not 
  admit 
  of 
  general 
  

   observation 
  and 
  application. 
  Lastly, 
  if 
  this 
  distinction 
  be 
  admitted, 
  

   it 
  will 
  become 
  a 
  question 
  whether 
  the 
  limits 
  of 
  Lonsdale's 
  genus 
  

   Stenopora 
  should 
  not 
  be 
  extended 
  so 
  as 
  to 
  receive 
  the 
  forms 
  gene- 
  

   rally 
  referred 
  to 
  Monticulipora. 
  

  

  The 
  presence 
  of 
  " 
  monticules 
  " 
  or 
  " 
  mamelons," 
  from 
  which 
  the 
  

   name 
  Monticulipora 
  was 
  derived, 
  cannot 
  be 
  relied 
  upon, 
  since 
  these 
  

   elevations 
  are 
  sometimes 
  wanting, 
  and, 
  besides, 
  vary 
  very 
  materially 
  

   in 
  their 
  nature 
  even 
  in 
  the 
  cases 
  where 
  they 
  present 
  themselves. 
  

  

  The 
  genus 
  Nebulipora, 
  M'Coy, 
  would 
  seem 
  to 
  have 
  been 
  rightly 
  

   included 
  by 
  Edwards 
  and 
  Haime 
  under 
  Monticulipora, 
  since 
  the 
  

   only 
  available 
  distinction 
  is 
  the 
  presence 
  of 
  mural 
  pores, 
  and 
  M'Coy 
  

   is 
  unable 
  to 
  speak 
  with 
  any 
  certainty 
  as 
  to 
  the 
  existence 
  of 
  these 
  

   openings 
  in 
  the 
  forms 
  upon 
  which 
  his 
  genus 
  is 
  founded. 
  

  

  For 
  the 
  reasons 
  above 
  given 
  I 
  shall 
  in 
  this 
  communication 
  place 
  

   all 
  the 
  corals 
  under 
  consideration 
  in 
  the 
  genus 
  Chcetetes, 
  irrespective 
  

   of 
  their 
  mode 
  of 
  increase, 
  which 
  is 
  in 
  many 
  instances 
  unknown. 
  

   The 
  specimens 
  from 
  which 
  my 
  descriptions 
  are 
  taken 
  have 
  been 
  

   partly 
  collected 
  by 
  myself 
  from 
  the 
  Hudson-Kiver 
  group 
  of 
  Canada 
  ; 
  

   but 
  most 
  of 
  them 
  have 
  been 
  kindly 
  furnished 
  to 
  me 
  from 
  the 
  

   Cincinnati 
  group 
  by 
  Mr. 
  James 
  and 
  Prof. 
  Orton, 
  and 
  from 
  the 
  

   Trenton 
  Limestone 
  by 
  Mr. 
  G. 
  J. 
  Hinde. 
  I 
  shall 
  also 
  not 
  only 
  

   describe 
  those 
  species 
  which 
  are 
  actually 
  new, 
  but 
  I 
  shall 
  likewise 
  

   give 
  a 
  brief 
  account 
  of 
  some 
  of 
  the 
  previously 
  recorded 
  species, 
  the 
  

   well-preserved 
  specimens 
  in 
  my 
  possession 
  in 
  many 
  cases 
  enabling 
  

   me 
  to 
  adduce 
  new 
  facts 
  of 
  interest 
  and 
  importance. 
  

  

  A 
  completely 
  satisfactory 
  subdivision 
  of 
  the 
  genus 
  Chcetetes 
  (in- 
  

   cluding 
  Monticulipora) 
  is 
  at 
  present 
  not 
  possible 
  ; 
  but 
  the 
  genus 
  

   may 
  be 
  conveniently 
  broken 
  up, 
  according 
  to 
  the 
  form 
  of 
  the 
  coral- 
  

   lum, 
  into 
  the 
  ramose, 
  frondescent, 
  massive, 
  and 
  incrusting 
  species. 
  

  

  I. 
  Eamose 
  Species. 
  

  

  This 
  group 
  includes 
  those 
  forms 
  in 
  which 
  the 
  corallum 
  is 
  ramose 
  

   or 
  dendroid, 
  the 
  corallites 
  disposed 
  in 
  a 
  radiating 
  manner 
  round 
  an 
  

   imaginary 
  axis. 
  The 
  corallum 
  is 
  rooted 
  at 
  the 
  base, 
  and 
  the 
  extre- 
  

   mities 
  of 
  the 
  branches 
  are 
  rounded. 
  Some 
  of 
  the 
  forms 
  of 
  this 
  

   group 
  are 
  slender 
  and 
  regularly 
  divided 
  ; 
  but 
  others 
  are 
  more 
  or 
  less 
  

   swollen 
  or 
  tumid 
  and 
  irregularly 
  branched, 
  becoming 
  sometimes 
  

   almost 
  lobate, 
  and 
  thus 
  passing 
  into 
  one 
  of 
  the 
  sections 
  of 
  the 
  

   massive 
  group. 
  

  

  1. 
  CHiETETES 
  Dalei, 
  Edw. 
  & 
  H. 
  PI. 
  XXIX. 
  figs. 
  1, 
  1 
  a. 
  

  

  Chcetetes 
  Dalei, 
  Edwards 
  & 
  Haime, 
  Pol. 
  Foss. 
  des 
  Terr. 
  Pale'oz. 
  

   pi. 
  19. 
  fig. 
  6. 
  

  

  Corallum 
  branching, 
  the 
  branches 
  cylindrical 
  or 
  elliptical, 
  dividing 
  

   dichotomously 
  at 
  short 
  intervals 
  ; 
  the 
  diameter 
  of 
  the 
  branches 
  on 
  

   an 
  average 
  from 
  3 
  to 
  4 
  lines, 
  but 
  sometimes 
  only 
  from 
  1 
  to 
  2 
  lines. 
  

   Calices 
  in 
  general 
  from 
  six 
  to 
  eight 
  in 
  the 
  space 
  of 
  1 
  line, 
  polygonal, 
  

  

  