﻿1863.] 
  DUNCAN 
  WEST 
  INDIAN 
  C0KAL6. 
  37 
  

  

  21. 
  Astilxa 
  beevis, 
  spec. 
  nov. 
  PI. 
  IV. 
  figs. 
  3 
  a, 
  3 
  b. 
  

  

  Corallum 
  small, 
  irregularly 
  convex 
  above, 
  and 
  slightly 
  concave 
  

   below. 
  Corallites 
  short, 
  irregularly 
  distant, 
  and 
  radiating. 
  Calices 
  

   circular, 
  tolerably 
  elevated, 
  their 
  height 
  varying 
  ; 
  the 
  margin 
  is 
  

   rather 
  sharp, 
  and 
  the 
  external 
  wall 
  is 
  marked 
  by 
  very 
  distinct 
  

   costae. 
  The 
  septa 
  are 
  very 
  slightly 
  exsert, 
  largest 
  at 
  the 
  wall, 
  arched, 
  

   the 
  radius 
  of 
  the 
  curve 
  being 
  directed 
  upwards 
  and 
  inwards, 
  

   passing 
  but 
  a 
  little 
  way 
  inwards 
  before 
  descending 
  abruptly 
  ; 
  they 
  

   are 
  dentate 
  on 
  the 
  free 
  margin. 
  In 
  six 
  systems 
  of 
  three 
  cycles, 
  

   with 
  a 
  septum 
  of 
  a 
  fourth 
  in 
  some 
  half-systems 
  ; 
  primary 
  septa 
  the 
  

   largest, 
  the 
  tertiary 
  being 
  small. 
  The 
  laminae 
  are 
  perfect, 
  join 
  the 
  

   columella 
  by 
  ascending 
  processes, 
  and 
  are 
  slightly 
  granular. 
  Costa3 
  

   well 
  developed, 
  passing 
  downwards 
  and 
  outwards 
  from 
  the 
  margin 
  : 
  

   the 
  primary 
  are 
  equal 
  to 
  the 
  secondary, 
  and 
  there 
  is 
  some 
  variation 
  

   in 
  the 
  size 
  of 
  the 
  tertiary 
  ; 
  they 
  are 
  dentate, 
  and 
  appear 
  to 
  be 
  covered 
  

   with 
  a 
  fine 
  epitheca, 
  and 
  their 
  course 
  is 
  often 
  in 
  a 
  curve. 
  In 
  trans- 
  

   verse 
  and 
  vertical 
  sections 
  the 
  costae 
  are 
  seen 
  to 
  project 
  far 
  from 
  the 
  

   wall, 
  and 
  to 
  be 
  marked 
  by 
  oblique 
  and 
  abundant 
  exothecal 
  dissepi- 
  

   ments 
  ; 
  the 
  tertiary 
  costae 
  being 
  much 
  less 
  projecting 
  than 
  the 
  others. 
  

   The 
  columella 
  is 
  large, 
  lax, 
  and 
  papillary. 
  The 
  fossa 
  is 
  deep. 
  The 
  

   endotheca 
  is 
  not 
  well 
  developed, 
  but 
  the 
  dissepiments 
  extend 
  to 
  close 
  

   to 
  the 
  calice. 
  Diameter 
  of 
  calices 
  -i- 
  inch 
  ; 
  height 
  of 
  the 
  corallum 
  

   -j^j 
  inch. 
  The 
  costae 
  are 
  very 
  marked 
  in 
  this 
  species, 
  and 
  with 
  the 
  

   papillary 
  columella 
  and 
  short 
  calices 
  distinguish 
  it 
  from 
  its 
  allies 
  ; 
  

   it 
  is 
  related 
  both 
  to 
  Astrcea 
  cylindrica, 
  nob., 
  and 
  to 
  Astrcea 
  cavernosa, 
  

   Edwards 
  & 
  Haime. 
  

  

  Prom 
  the 
  Nivaje 
  shale, 
  San 
  Domingo. 
  Coll. 
  Geol. 
  Soc. 
  

  

  Amongst 
  the 
  specimens 
  from 
  the 
  silt 
  of 
  the 
  Sandstone 
  plain 
  of 
  San 
  

   Domingo, 
  there 
  are 
  four 
  well-marked 
  species 
  of 
  a 
  genus 
  hardly 
  as 
  yet 
  

   recognized 
  as 
  belonging 
  to 
  the 
  present 
  West 
  Indian 
  Coral-fauna*, 
  but 
  

   which 
  is 
  well 
  known 
  in 
  that 
  of 
  the 
  Indian 
  Ocean, 
  South 
  Sea, 
  and 
  

   Pacific. 
  A 
  fossil 
  species 
  has 
  been 
  described 
  from 
  the 
  Saucats 
  Miocene, 
  

   Plesiastrcea 
  Desmoulinsi, 
  Edwards 
  & 
  Haime, 
  op. 
  cit. 
  p. 
  492, 
  and 
  the 
  

   new 
  forms 
  are 
  found 
  in 
  various 
  degrees 
  of 
  fossilization. 
  These 
  San- 
  

   Domingan 
  species 
  f 
  form, 
  with 
  one 
  exception, 
  a 
  subgenus; 
  they 
  are 
  

   globular 
  in 
  shape, 
  and 
  there 
  is 
  usually 
  much 
  distance 
  between 
  the 
  

   corallites, 
  the 
  interval 
  not 
  being 
  filled 
  by 
  costae, 
  but 
  with 
  an 
  amount 
  

   of 
  exotheca 
  which 
  is 
  Solenastraean 
  in 
  its 
  development, 
  for 
  the 
  costae 
  

   are 
  very 
  small, 
  and 
  the 
  coenenchymatous 
  cells 
  are 
  largely 
  developed. 
  

  

  22. 
  Plesiastilea 
  distans, 
  spec. 
  nov. 
  PL 
  IV. 
  figs. 
  4 
  a, 
  4b. 
  

  

  Corallum 
  globular, 
  with 
  a 
  very 
  small 
  surface 
  of 
  former 
  adherence 
  

   below, 
  and 
  with 
  a 
  slightly 
  gibbous 
  calicular 
  surface. 
  Calices 
  wide 
  

   apart, 
  circular, 
  but 
  slightly 
  elevated 
  above 
  the 
  surface, 
  which 
  is 
  

  

  * 
  Duchassaing 
  and 
  Michelotti 
  (Mem. 
  Acad. 
  Turin, 
  2nd 
  ser. 
  vol. 
  xix. 
  p. 
  279, 
  

   1861) 
  describe 
  a 
  species 
  of 
  Plesiastrcea 
  (recent) 
  from 
  St. 
  Thornas, 
  but 
  do 
  not 
  give 
  

   a 
  figure. 
  Milne-Edwards 
  does 
  not 
  describe 
  any 
  West 
  Indian 
  species. 
  

  

  f 
  They 
  are 
  very 
  remotely 
  allied 
  to 
  the 
  species 
  from 
  St. 
  Thomas, 
  

  

  