﻿510 
  H. 
  ALLEYNE 
  NICHOLSON 
  ON 
  SPECIES 
  OE 
  CH^TETES 
  

  

  lum 
  is 
  more 
  or 
  less 
  deeply 
  concave 
  ; 
  others 
  are 
  fixed 
  to 
  some 
  

   foreign 
  object 
  ; 
  and 
  the 
  mode 
  of 
  existence 
  of 
  other 
  examples 
  is 
  

   unknown. 
  

  

  15. 
  Ch^tetes 
  peteopolitanus, 
  Pander. 
  PI. 
  XXX. 
  figs. 
  5-5 
  c, 
  6, 
  7, 
  8. 
  

  

  Favosites 
  petropolitanus, 
  Pander, 
  Puss. 
  Peiche, 
  pi. 
  1. 
  figs. 
  6, 
  7, 
  

   10, 
  11. 
  

  

  Favosites 
  lycopodites, 
  Yanuxem, 
  Geol. 
  New 
  York, 
  3rd 
  part, 
  p. 
  46, 
  

   fig. 
  3. 
  

  

  Chastetes 
  petropolitanus, 
  Lonsdale, 
  in 
  Murch. 
  Vern. 
  & 
  Keys. 
  Puss. 
  

   & 
  Ural, 
  vol. 
  i. 
  pi. 
  A. 
  fig. 
  10. 
  

  

  Chcetetes 
  ly 
  coper 
  don, 
  Hall 
  (ex 
  parte), 
  Pal. 
  X. 
  Y. 
  vol. 
  i. 
  pi. 
  23. 
  fig. 
  1, 
  

   and 
  pi. 
  24. 
  figs. 
  1 
  a-h, 
  also 
  vol. 
  ii. 
  pi. 
  17. 
  figs. 
  1 
  a-f. 
  

  

  Monticulipora 
  petropolitana, 
  Edw. 
  & 
  Haime, 
  Prit. 
  Foss. 
  Corals, 
  

   p. 
  264. 
  

  

  Chcetetes 
  petropolitanus, 
  Meek 
  & 
  Worthen, 
  Geol. 
  Illinois, 
  vol. 
  iii. 
  

   pi. 
  2. 
  figs. 
  8 
  a, 
  b. 
  

  

  (Only 
  the 
  more 
  important 
  portion 
  of 
  the 
  synonymy 
  of 
  this 
  species 
  

   is 
  here 
  given.) 
  

  

  " 
  Corallum 
  in 
  general 
  free 
  ; 
  its 
  basal 
  plate 
  flat 
  or 
  concave, 
  and 
  

   completely 
  covered 
  with 
  a 
  concentrically 
  wrinkled 
  epitheca. 
  Upper 
  

   surface 
  regularly 
  convex, 
  in 
  general 
  hemispherical, 
  and 
  presenting 
  

   obtuse 
  tuberosities 
  about 
  1 
  line 
  broad 
  and 
  varying 
  very 
  much 
  in 
  

   height. 
  In 
  some 
  specimens 
  these 
  tubercles 
  appear 
  to 
  have 
  been 
  

   worn 
  away, 
  and 
  their 
  existence 
  is 
  indicated 
  only 
  by 
  the 
  presence 
  of 
  

   small 
  groups 
  of 
  large 
  calices, 
  witb 
  thick 
  walls 
  ; 
  the 
  calices 
  are 
  rather 
  

   unequal 
  in 
  size, 
  generally 
  polygonal, 
  sometimes 
  almost 
  circular 
  ; 
  the 
  

   largest 
  are 
  about 
  one 
  fifth 
  of 
  a 
  line 
  in 
  diameter 
  ; 
  the 
  walls 
  are 
  not 
  

   perforated 
  ; 
  the 
  tabulae 
  are 
  horizontal, 
  complete, 
  and 
  placed 
  at 
  

   about 
  one 
  twelfth 
  of 
  a 
  line 
  from 
  each 
  other. 
  Some 
  vestiges 
  of 
  septa 
  

   are 
  often 
  visible. 
  Young 
  specimens 
  are 
  fiat 
  and 
  discoidal." 
  (Ed- 
  

   wards 
  & 
  Ptaime, 
  Prit. 
  Foss. 
  Corals, 
  p. 
  265.) 
  

  

  The 
  Trenton 
  Limestone 
  and 
  Hudson-Piver 
  group 
  yield 
  a 
  great 
  

   many 
  examples 
  which 
  correspond 
  with 
  the 
  above 
  description 
  in 
  

   essential 
  respects 
  — 
  some 
  altogether 
  so, 
  but 
  others 
  with 
  more 
  or 
  less 
  

   striking 
  variations. 
  In 
  form 
  this 
  species 
  is 
  protean, 
  being 
  more 
  or 
  

   less 
  discoidal 
  when 
  young, 
  but 
  being 
  iu 
  its 
  adult 
  state 
  subspherical, 
  

   hemispherical, 
  subpyriform, 
  lobate, 
  mushroom-shaped, 
  or 
  shaped 
  

   somewhat 
  like 
  a 
  cardinal's 
  hat. 
  The 
  surface 
  is 
  sometimes 
  mammil- 
  

   lated 
  with 
  obtuse 
  tubercles 
  or 
  elevations 
  of 
  different 
  sizes 
  and 
  vari- 
  

   able 
  height 
  ; 
  but 
  quite 
  commonly 
  it 
  is 
  perfectly 
  smooth, 
  especially 
  

   in 
  the 
  smaller 
  examples. 
  Often 
  no 
  definite 
  groups 
  of 
  large- 
  sized 
  

   corallites 
  can 
  be 
  recognized 
  ; 
  but 
  at 
  other 
  times 
  such 
  are 
  present. 
  

   In 
  all 
  the 
  specimens 
  that 
  have 
  come 
  under 
  my 
  notice 
  the 
  calices 
  

   are 
  polygonal 
  or 
  subpolygonal, 
  generally 
  about 
  ten 
  in 
  the 
  space 
  of 
  

   one 
  line, 
  sometimes 
  fewer, 
  without 
  any 
  very 
  minute 
  tubuli 
  interca- 
  

   lated 
  amongst 
  them. 
  

  

  Pesides 
  the 
  typical 
  free-living 
  examples 
  of 
  this 
  species, 
  with 
  a 
  con- 
  

   cave 
  base 
  and 
  concentrically 
  wrinkled 
  epitheca, 
  the 
  Cincinnati 
  group 
  

   yields 
  a 
  number 
  of 
  small, 
  hemispherical, 
  subspherical, 
  smooth 
  or 
  

  

  