﻿WRIGHT 
  AND 
  ADAMS 
  MALTESE 
  ECHTNODERMS. 
  489 
  

  

  which 
  is 
  broadly 
  and 
  sharply 
  truncated 
  ; 
  in 
  the 
  upper 
  half 
  of 
  this 
  

   space 
  the 
  large 
  transversely 
  oval 
  vent 
  is 
  found. 
  The 
  base 
  is 
  flat 
  ; 
  

   the 
  plastron 
  has 
  a 
  raised 
  ridge 
  in 
  the 
  middle 
  line, 
  and 
  the 
  basal 
  

   portion 
  of 
  all 
  the 
  interambulacra 
  are 
  covered 
  with 
  large 
  tubercles 
  ; 
  

   the 
  naked 
  spaces 
  on 
  each 
  side 
  of 
  the 
  plastron 
  correspond 
  with 
  the 
  

   posterior 
  ambulacra. 
  

  

  Affinities 
  and 
  differences. 
  — 
  S. 
  delphinus 
  resembles 
  S. 
  Desmaresti, 
  

   but 
  is 
  proportionately 
  shorter 
  and 
  broader 
  ; 
  the 
  petaloid 
  ambulacra 
  

   are 
  longer 
  and 
  narrower, 
  and 
  the 
  external 
  rows 
  of 
  the 
  poriferous 
  

   zones 
  have 
  smaller 
  pores 
  near 
  the 
  summit 
  ; 
  the 
  dorsal 
  ridge 
  is 
  much 
  

   more 
  arched 
  and 
  prominent, 
  and 
  the 
  truncation 
  of 
  the 
  posterior 
  

   border 
  much 
  greater. 
  

  

  Locality 
  and 
  Stratigraphical 
  'position. 
  — 
  A 
  large 
  specimen 
  has 
  been 
  

   obtained 
  from 
  the 
  No. 
  1 
  (the 
  Upper 
  Limestone), 
  and 
  a 
  smaller 
  form 
  

   from 
  No. 
  2 
  (the 
  yellow 
  sand) 
  at 
  Malta. 
  

  

  M. 
  Defrance's 
  specimen 
  came 
  from 
  the 
  Molasse 
  of 
  St. 
  -Paul 
  - 
  

   Trois- 
  Chateaux. 
  

  

  Collections. 
  — 
  Museum 
  of 
  the 
  Geological 
  Society 
  ; 
  my 
  cabinet. 
  

  

  37. 
  Sfatangus 
  pustuloses, 
  "Wright, 
  sp. 
  nov. 
  PI. 
  XXI. 
  fig. 
  2. 
  

  

  Test 
  cordate 
  ; 
  anterior 
  border 
  widely 
  grooved 
  ; 
  anteal 
  sulcus 
  deep 
  ; 
  

   petaloid 
  ambulacra 
  long, 
  nearly 
  equal, 
  and 
  concave 
  ; 
  the 
  five 
  upper 
  

   plates 
  of 
  all 
  the 
  interambulacra 
  with 
  groups 
  of 
  large 
  tubercles 
  on 
  

   each 
  ; 
  apical 
  disk 
  small, 
  excentral 
  ; 
  four 
  genital 
  pores 
  ; 
  posterior 
  border 
  

   truncated 
  ; 
  base 
  rounded 
  before, 
  with 
  a 
  prominent 
  convex 
  plastron. 
  

  

  Dimensions. 
  — 
  Antero 
  -posterior 
  diameter 
  ly 
  7 
  ^- 
  inch 
  ; 
  transverse 
  dia- 
  

   meter 
  1^ 
  inch 
  ; 
  height 
  -^ 
  inch. 
  

  

  Description. 
  — 
  The 
  wide 
  groove 
  in 
  the 
  front 
  border, 
  and 
  the 
  groups 
  

   of 
  large 
  pustular-looking 
  tubercles 
  on 
  the 
  five 
  uj>permost 
  plates 
  of 
  

   all 
  the 
  interambulacra, 
  form 
  the 
  diagnostic 
  characters 
  of 
  this 
  species. 
  

   The 
  petaloid 
  ambulacra 
  are 
  nearly 
  equal 
  in 
  size 
  ; 
  they 
  are 
  long, 
  straight, 
  

   and 
  concave, 
  the 
  anterior 
  pair 
  being 
  gently 
  flexed 
  forwards 
  and 
  

   outwards, 
  whilst 
  the 
  posterior 
  pair 
  are 
  directed 
  backwards. 
  The 
  

   poriferous 
  zones 
  are 
  half 
  as 
  wide 
  as 
  the 
  internal 
  spaces 
  ; 
  the 
  small 
  

   apical 
  disk 
  is 
  excentral, 
  with 
  four 
  ovarian 
  holes, 
  the 
  spongy 
  madrepo- 
  

   riform 
  body 
  occupying 
  the 
  middle 
  ; 
  the 
  surface 
  of 
  the 
  plates 
  is 
  covered 
  

   with 
  very 
  small 
  tubercles 
  set 
  closely 
  together, 
  which 
  contrast 
  strongly 
  

   with 
  the 
  large 
  dorsal 
  tubercles 
  of 
  the 
  interambulacra 
  ; 
  the 
  posterior 
  

   border 
  is 
  slightly 
  truncated, 
  and 
  the 
  vent 
  occupies 
  the 
  upper 
  half 
  of 
  

   the 
  section 
  ; 
  the 
  base 
  is 
  slightly 
  convex 
  anteriorly, 
  but 
  largely 
  so 
  

   posteriorly 
  ; 
  from 
  the 
  prominence 
  and 
  convexity 
  of 
  the 
  plastron, 
  the 
  

   true 
  position 
  of 
  the 
  peristome 
  cannot 
  be 
  ascertained 
  in 
  consequence 
  of 
  

   the 
  fracture 
  in 
  the 
  base 
  of 
  the 
  most 
  perfect 
  specimen. 
  

  

  Affinities 
  and 
  differences. 
  — 
  The 
  diagnosis 
  of 
  this 
  species 
  has 
  been 
  

   already 
  pointed 
  out 
  ; 
  it 
  differs 
  from 
  all 
  its 
  known 
  congeners 
  in 
  the 
  

   width 
  of 
  the 
  groove, 
  in 
  its 
  anterior 
  border, 
  and 
  the 
  regular 
  grouping 
  

   of 
  its 
  large 
  tubercles. 
  

  

  Locality 
  and 
  Stratigraphical 
  position. 
  — 
  Collected 
  from 
  bed 
  No. 
  4. 
  

   The 
  only 
  specimens 
  I 
  know 
  are 
  those 
  belonging 
  to 
  the 
  Museum 
  of 
  

   the 
  Geological 
  Society. 
  

  

  