﻿E. 
  E. 
  TOMES 
  OX 
  LOWEE-OOLITE 
  MADEEPOEAEIA. 
  435 
  

  

  urination 
  which 
  has 
  been 
  exercised 
  on 
  the 
  allied 
  genera 
  Thamnas- 
  

   trcea 
  and 
  Microsolena 
  ; 
  and 
  the 
  result 
  has 
  been 
  its 
  establishment 
  as 
  

   a 
  subgenus. 
  

  

  There 
  seems 
  no 
  doubt 
  that 
  it 
  corresponds 
  with 
  the 
  subgenus 
  Oen- 
  

   tmstrcea, 
  proposed 
  by 
  de 
  Fromentel 
  in 
  1858-61* 
  ; 
  and 
  therefore, 
  

   while 
  we 
  adopt 
  the 
  name 
  of 
  Synastrcea, 
  proposed 
  by 
  de 
  Fromentel, 
  

   for 
  such 
  Thamnastrasce 
  as 
  have 
  a 
  spongy 
  columella, 
  we 
  must 
  also 
  make 
  

   use 
  of 
  the 
  name 
  of 
  AstroeomorpJia, 
  given 
  by 
  Reuss 
  to 
  those 
  which 
  are 
  

   characterized 
  by 
  the 
  existence 
  of 
  a 
  stylif 
  orm 
  columella. 
  

  

  The 
  true 
  Thamnastrcece 
  would 
  then 
  be 
  those 
  which 
  have 
  no 
  

   columella. 
  

  

  Subgenus 
  Syxaste^a, 
  de 
  Prom. 
  

   Thajixastb^a 
  (Syxaste^a) 
  ceickleyexsis, 
  n. 
  sp. 
  

  

  The 
  corallum 
  has 
  a 
  depressed 
  form, 
  the 
  under 
  surface 
  being 
  a 
  

   little 
  convex, 
  with 
  a 
  sub 
  central 
  prominent 
  part, 
  which 
  was 
  a 
  point 
  

   of 
  attachment. 
  The 
  upper 
  surface 
  is 
  flat, 
  and 
  presents 
  an 
  oblong 
  

   figure, 
  which 
  is 
  somewhat 
  kidney-shaped, 
  with 
  the 
  outer 
  edge 
  thin 
  

   and 
  a 
  little 
  undulating. 
  

  

  The 
  epitheca 
  is 
  rudimentary 
  and 
  disposed 
  in 
  rings 
  ; 
  but 
  as 
  there 
  

   is 
  much 
  more 
  of 
  it 
  on 
  one 
  side 
  of 
  the 
  corallum 
  than 
  the 
  other, 
  it 
  is 
  

   probable 
  that 
  it 
  has 
  been 
  equally 
  developed, 
  but 
  since 
  destroyed. 
  

  

  The 
  mural 
  costoe 
  are 
  thin, 
  straight, 
  uniform, 
  and 
  parallel. 
  Their 
  

   thickness 
  is 
  not 
  more 
  than 
  half 
  the 
  width 
  of 
  the 
  interval 
  between 
  

   them. 
  Their 
  synapticulae 
  are 
  distinct, 
  though 
  not 
  strongly 
  de- 
  

   veloped. 
  

  

  The 
  calices 
  ere 
  evenly 
  scattered 
  over 
  the 
  upper 
  surface. 
  They 
  

   are 
  rounded, 
  with 
  a 
  distinct 
  disposition 
  towards 
  a 
  quadrangular 
  

   form 
  ; 
  and 
  the 
  costae 
  between 
  them 
  form 
  ridges, 
  which 
  give 
  to 
  the 
  

   calices 
  much 
  the 
  appearance 
  of 
  those 
  of 
  the 
  Isastrczce. 
  The 
  distance 
  

   from 
  centre 
  to 
  centre 
  of 
  the 
  calices 
  is 
  from 
  2 
  to 
  2| 
  lines. 
  

  

  The 
  septa 
  and 
  septal 
  costse 
  are 
  thick 
  ; 
  and 
  the 
  latter 
  are 
  almost 
  in 
  

   contact 
  with 
  each 
  other 
  laterally, 
  where 
  they 
  join 
  those 
  of 
  other 
  

   calices, 
  with 
  which 
  they 
  form 
  a 
  more 
  or 
  less 
  obtuse 
  angle. 
  They 
  

   decrease 
  in 
  thickness 
  inwards 
  as 
  they 
  approach 
  the 
  columella, 
  into 
  

   which 
  they 
  blend. 
  The 
  point 
  at 
  which 
  the 
  septa 
  pass 
  into 
  and 
  be- 
  

   come 
  septal 
  costae 
  is 
  often 
  indicated 
  by 
  the 
  latter 
  becoming 
  forked. 
  

   All 
  these 
  have 
  lost 
  their 
  upper 
  margins 
  and 
  become 
  smooth. 
  From 
  

   twelve 
  to 
  sixteen 
  septa 
  occur 
  in 
  each 
  calice, 
  being 
  two 
  cycles 
  and 
  

   the 
  rudiments 
  of 
  a 
  third. 
  

  

  The 
  columella, 
  when 
  the 
  calices 
  are 
  not 
  much 
  worn, 
  is 
  small, 
  but 
  

   well 
  denned, 
  and 
  consists 
  of 
  a 
  number 
  of 
  papillas, 
  varying 
  from 
  three 
  

   or 
  four 
  to 
  seven 
  or 
  eight. 
  When 
  the 
  calices 
  are 
  much 
  worn 
  down 
  it 
  

   is 
  of 
  greater 
  size, 
  and 
  presents 
  the 
  appearance 
  of 
  a 
  spongy 
  mass. 
  

  

  This 
  new 
  species 
  has 
  been 
  met 
  with 
  once 
  at 
  Crickley 
  Hill. 
  The 
  

   specimen 
  was 
  a 
  dead 
  one, 
  with 
  all 
  the 
  calicular 
  surface 
  more 
  or 
  

   less 
  worn 
  down 
  and 
  partially 
  obscured 
  by 
  a 
  growth 
  of 
  delicate 
  

   Bryozoa 
  before 
  fossilization 
  took 
  place. 
  

  

  It 
  is 
  to 
  Thamnastrcea 
  arachnoides 
  of 
  the 
  Coral 
  Eag 
  that 
  the 
  

   * 
  Introd. 
  Etude 
  Polyp. 
  Foss. 
  p. 
  215 
  (1858-61). 
  

  

  