﻿E. 
  F. 
  TOMES 
  ON 
  LOWEE-OOLITE 
  MADEEPOEAEIA. 
  437 
  

  

  men. 
  It 
  was 
  taken 
  by 
  me 
  from 
  the 
  Trigonia-grit 
  at 
  Ravens- 
  

   gate 
  Hill. 
  The 
  only 
  difference 
  between 
  it 
  and 
  the 
  specimen 
  which 
  

   supplied 
  Prof. 
  Duncan's 
  figure 
  is 
  in 
  the 
  septa 
  and 
  septal 
  costae, 
  

   which 
  are 
  more 
  uniform 
  in 
  thickness 
  in 
  my 
  specimen 
  than 
  they 
  are 
  

   shown 
  to 
  be 
  in 
  the 
  figure. 
  That 
  difference, 
  however, 
  is 
  most 
  likely 
  

   due 
  to 
  those 
  parts 
  having 
  been 
  less 
  worn 
  down 
  in 
  the 
  one 
  from 
  

   Ravensgate 
  than 
  in 
  the 
  type 
  specimen. 
  

  

  Thamnaste^a 
  Lyelli, 
  Edw. 
  & 
  Haime, 
  Brit. 
  Eoss. 
  Cor. 
  pt. 
  ii. 
  

   p. 
  118, 
  pi. 
  xxi. 
  fig. 
  4. 
  1851. 
  

  

  MM. 
  Edwards 
  and 
  Haime 
  mention 
  a 
  cast 
  found 
  near 
  Bath 
  by 
  

   Mr. 
  Bowerbank 
  which 
  they 
  refer 
  to 
  this 
  species, 
  but 
  observe 
  that 
  

   the 
  calices 
  are 
  smaller 
  and 
  more 
  crowded 
  than 
  in 
  the 
  specimens 
  from 
  

   Stonesfield. 
  

  

  Compared 
  with 
  Stonesfield 
  examples, 
  I 
  find 
  that 
  the 
  Gloucester- 
  

   shire 
  ones 
  present 
  precisely 
  the 
  same 
  differences 
  which 
  are 
  here 
  

   mentioned. 
  But 
  they 
  also 
  have 
  the 
  septa 
  and 
  septal 
  costae 
  more 
  

   exsert, 
  becoming 
  on 
  the 
  smaller 
  branches 
  subcristiform, 
  with 
  their 
  

   papillae 
  placed 
  transversely. 
  The 
  cycles 
  of 
  the 
  septa 
  are 
  just 
  as 
  in 
  

   the 
  typical 
  Thamnastrcea 
  Lyelli. 
  

  

  I 
  do 
  not 
  think 
  the 
  differences 
  here 
  indicated 
  sufficient 
  to 
  con- 
  

   stitute 
  a 
  new 
  species. 
  

  

  The 
  basal 
  portion 
  of 
  a 
  specimen 
  from 
  Crickley 
  Hill, 
  showing 
  the 
  

   attachment, 
  measures 
  \\ 
  inch 
  in 
  diameter. 
  Fragments 
  of 
  all 
  sizes 
  

   are 
  to 
  be 
  met 
  with 
  both 
  at 
  Crickley 
  Hill, 
  in 
  the 
  lower 
  reef, 
  and 
  at 
  

   Leckhampton 
  Hill, 
  in 
  the 
  middle 
  reef. 
  

  

  I 
  have 
  entertained 
  some 
  doubt 
  about 
  the 
  real 
  affinities 
  of 
  this 
  

   species, 
  and 
  am 
  by 
  no 
  means 
  satisfied 
  that 
  it 
  is 
  really 
  a 
  Thamnastrcea. 
  

   In 
  some 
  examples, 
  whether 
  from 
  the 
  Inferior 
  Oolite 
  or 
  the 
  Great 
  

   Oolite 
  of 
  Stonesfield, 
  from 
  which 
  place 
  the 
  type 
  specimens 
  were 
  

   taken, 
  there 
  is 
  often 
  an 
  indication 
  of 
  a 
  circular 
  calice, 
  which 
  was 
  

   hidden 
  until 
  the 
  costae 
  were 
  worn 
  away. 
  At 
  no 
  age 
  nor 
  in 
  any 
  

   state 
  of 
  preservation 
  have 
  I 
  succeeded 
  in 
  detecting 
  synapticulae. 
  If 
  

   it 
  is 
  one 
  of 
  the 
  Astraeidae, 
  it 
  is 
  to 
  the 
  genus 
  Conveceastrcm 
  that 
  it 
  is 
  

   most 
  nearly 
  allied, 
  though 
  it 
  possesses 
  a 
  columella. 
  

  

  Thamnastejea 
  Weighti, 
  n. 
  sp. 
  (PI. 
  XVIII. 
  fig. 
  14.) 
  

  

  The 
  corallum 
  is 
  oblong 
  or 
  rounded, 
  always 
  more 
  or 
  less 
  de- 
  

   pressed, 
  and 
  has 
  the 
  calicular 
  surface 
  varying 
  from 
  a 
  slight 
  degree 
  

   of 
  concavity 
  to 
  a 
  flat 
  or 
  slightly 
  convex 
  surface. 
  Generally 
  the 
  

   under 
  surface 
  has 
  a 
  little 
  convexity, 
  with 
  a 
  central 
  prominent 
  point 
  

   of 
  attachment 
  ; 
  but 
  it 
  is 
  sometimes 
  flat, 
  or 
  even 
  concave, 
  with 
  the 
  

   same 
  prominent 
  part. 
  In 
  one 
  instance 
  only 
  have 
  I 
  seen 
  it 
  with 
  a 
  

   height 
  greater 
  than 
  the 
  base, 
  formed 
  by 
  layer 
  upon 
  layer. 
  

  

  The 
  epitheca 
  is 
  generally 
  rudimentary, 
  seldom 
  appearing 
  as 
  more 
  

   than 
  a 
  succession 
  of 
  concentric 
  bands, 
  and 
  it 
  is 
  often 
  absent- 
  

   altogether. 
  

  

  The 
  mural 
  costae 
  are 
  distinct, 
  straight, 
  delicate, 
  and 
  connected 
  by 
  

   numerous 
  oblique 
  synapticulae. 
  

  

  The 
  calices 
  are 
  small, 
  and 
  scattered 
  without 
  order 
  over 
  the 
  upper 
  

  

  