﻿478 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  8. 
  Cltpe 
  aster 
  marginatus, 
  Lamarck. 
  

  

  Stratir/raphical 
  position. 
  — 
  Collected 
  at 
  Malta 
  from. 
  the 
  Sand-bed 
  

   No. 
  2. 
  It 
  is 
  found 
  likewise 
  in 
  the 
  Miocene 
  beds 
  of 
  Touraine, 
  Landes, 
  

   Narosse, 
  Dax, 
  Bonifacio, 
  Santa 
  Maura, 
  and 
  Corsica. 
  

  

  Collections. 
  — 
  British 
  Museum 
  ; 
  Royal 
  School 
  of 
  Mines 
  ; 
  Geological 
  

   Society 
  ; 
  Bristol 
  Museum 
  ; 
  Earl 
  of 
  Ducie's 
  collection 
  ; 
  my 
  cabinet. 
  

  

  9. 
  Clype 
  aster 
  Reidii, 
  Wright. 
  

  

  Locality 
  and 
  Stratigraphical 
  position. 
  — 
  This 
  species 
  is 
  from 
  bed 
  

   No. 
  1, 
  the 
  Upper 
  Limestone. 
  Fine 
  specimens 
  are 
  in 
  the 
  Museum 
  

   of 
  the 
  Royal 
  School 
  of 
  Mines 
  and 
  in 
  the 
  collection 
  of 
  the 
  Geological 
  

   Society 
  of 
  London. 
  The 
  type 
  -specimen 
  in 
  my 
  collection 
  has 
  been 
  

   figured 
  by 
  M. 
  Michelin 
  in 
  his 
  beautiful 
  monograph 
  of 
  Fossil 
  Cly- 
  

   peasters. 
  

  

  10. 
  Clypeaster 
  portentosus, 
  Desmoulins. 
  

  

  Clypeaster 
  portentosus, 
  Desm. 
  Etudes 
  des 
  Echinides, 
  1835, 
  p. 
  218. 
  

   C. 
  Agassizi, 
  Sismonda, 
  Suppl. 
  Echin. 
  Foss. 
  di 
  Nizza, 
  1842, 
  p. 
  48. 
  

   C. 
  alius, 
  var. 
  turrita, 
  Ag. 
  & 
  Desor, 
  Cat. 
  Echinides, 
  1846, 
  p. 
  72. 
  

   C. 
  turritus 
  et 
  altus, 
  Desor, 
  Synopsis 
  des 
  Echinides 
  Foss., 
  1858, 
  

   p. 
  240. 
  

  

  C. 
  portentosus, 
  Michelin, 
  Monogr. 
  des 
  Clypeastres 
  Foss. 
  1861,pl.48. 
  

  

  Form 
  in 
  general 
  nearly 
  regularly 
  pentagonal, 
  very 
  much 
  elevated 
  

   in 
  the 
  centre 
  ; 
  border 
  thick 
  and 
  round, 
  about 
  one 
  -third 
  of 
  the 
  total 
  

   height 
  ; 
  upper 
  surface 
  forming 
  an 
  elevated 
  pyramid, 
  sometimes 
  

   inclined 
  to 
  one 
  side 
  ; 
  the 
  length 
  of 
  the 
  sides 
  nearly 
  equal 
  to 
  the 
  

   height 
  of 
  the 
  pyramid; 
  under 
  surface 
  flat, 
  mouth-opening 
  deeply 
  

   sunk 
  ; 
  the 
  ambulacral 
  grooves 
  disappear 
  near 
  the 
  border 
  ; 
  summit 
  

   irregular, 
  sometimes 
  one 
  of 
  the 
  ambulacra 
  rises 
  higher 
  than 
  the 
  others. 
  

   Madreporiform 
  body 
  small, 
  pentagonal, 
  surrounded 
  by 
  the 
  elevated 
  

   ambulacra 
  which 
  rise 
  above 
  its 
  surface 
  ; 
  genital 
  plates 
  small, 
  ocular 
  

   plates 
  nearly 
  concealed 
  ; 
  ambulacral 
  areas 
  elongated, 
  large 
  and 
  

   prominent 
  throughout, 
  petaloid, 
  and 
  widely 
  open 
  below 
  ; 
  poriferous 
  

   zones 
  wide, 
  composed 
  of 
  sulci 
  terminating 
  in 
  pores 
  ; 
  septa 
  large, 
  

   with 
  from 
  6 
  to 
  10 
  tubercles 
  ; 
  interporiferous 
  zones 
  semicylindrical 
  ; 
  

   interambulacral 
  areas 
  narrow, 
  less 
  prominent 
  than 
  the 
  ambulacral 
  ; 
  

   peristome 
  in 
  a 
  deep 
  concavity, 
  pentagonal, 
  with 
  narrow 
  ambulacral 
  

   sulci 
  radiating 
  from 
  the 
  five 
  angles 
  ; 
  vent 
  inframarginal. 
  

  

  Dimensions. 
  — 
  Length 
  5 
  T 
  4 
  y- 
  inches 
  ; 
  transverse 
  diameter 
  4J 
  inches 
  ; 
  

   height 
  3f 
  inches. 
  

  

  Affinities 
  and 
  differences. 
  — 
  It 
  resembles 
  O. 
  pyramidalis, 
  Mich., 
  

   but 
  differs, 
  according 
  to 
  M. 
  Michelin, 
  by 
  the 
  pyramidal 
  elevation 
  of 
  

   the 
  ambulacral 
  zones 
  and 
  the 
  smallness 
  of 
  the 
  summit. 
  

  

  Strath 
  J 
  raphical 
  position. 
  — 
  Collected 
  at 
  Malta 
  from 
  the 
  Sand-bed 
  

   No. 
  2, 
  where 
  it 
  is 
  not 
  uncommon. 
  It 
  is 
  likewise 
  found 
  in 
  the 
  

   Miocene 
  of 
  Dax, 
  Landes, 
  Eisenstadt, 
  and 
  Isle 
  of 
  Capri. 
  

  

  Collections.— 
  British 
  Museum 
  ; 
  Royal 
  School 
  of 
  Mines 
  ; 
  Geological 
  

   Society 
  ; 
  my 
  cabinet. 
  

  

  