﻿Mr. 
  J. 
  W. 
  Gregory 
  on 
  Zeuglopleurus. 
  495 
  

  

  meet 
  tlie 
  adjoining 
  basals 
  on 
  each 
  side 
  of 
  them, 
  and 
  thus 
  the 
  

   antero- 
  lateral 
  and 
  anterior 
  radials 
  are 
  excluded 
  from 
  the 
  anal 
  

   ring, 
  while 
  the 
  anus 
  is 
  pushed 
  towards 
  the 
  posterior 
  side; 
  the 
  

   posterior 
  basal 
  is 
  very 
  narrow. 
  All 
  the 
  ten 
  plates 
  are 
  per- 
  

   forated. 
  

  

  Ambulacra 
  (figs. 
  3 
  and 
  5) 
  somewhat 
  narrow 
  and 
  straight 
  

   Each 
  bears 
  one 
  or 
  two 
  rows 
  of 
  primary 
  tubercles, 
  which 
  are 
  

   crenulate 
  and 
  imperforate 
  and 
  surrounded 
  by 
  small 
  scrobicular 
  

   areas, 
  broken 
  by 
  series 
  of 
  radiating 
  costulate 
  ridges 
  which 
  unite 
  

   with 
  those 
  of 
  the 
  adjoining 
  plates 
  above 
  and 
  below. 
  The 
  rest 
  

   of 
  the 
  plate 
  is 
  covered 
  with 
  miliary 
  granules 
  arranged 
  with 
  

   some 
  regularity. 
  The 
  horizontal 
  sutures 
  are 
  notched 
  by 
  

   grooves, 
  much 
  as 
  in 
  Glyphocyphus, 
  which 
  affect 
  especially 
  

   the 
  adoral 
  edge 
  of 
  the 
  plates, 
  so 
  that 
  the 
  lower 
  plate 
  projects 
  

   above 
  the 
  upper 
  one. 
  

  

  Structure 
  of 
  the 
  poriferous 
  zones 
  (fig. 
  5). 
  — 
  The 
  pairs 
  of 
  

   pores 
  are 
  in 
  single 
  rows, 
  which 
  are 
  nearly 
  straight. 
  The 
  

   plates 
  nearest 
  the 
  disk 
  are 
  primaries, 
  but, 
  proceeding 
  actinally, 
  

   they 
  become 
  fused 
  to 
  form 
  compound 
  plates 
  of 
  two 
  or 
  three 
  

   primaries 
  ; 
  a 
  single 
  primary 
  is 
  often 
  intercalated 
  between 
  two 
  

   compound 
  plates. 
  

  

  Inter 
  ambulacra 
  (fig. 
  4) 
  about 
  one 
  and 
  a 
  half 
  times 
  as 
  wide 
  

   as 
  the 
  ambulacra; 
  the 
  epistroma 
  is 
  similar 
  to 
  that 
  on 
  the 
  

   ambulacral 
  plates, 
  but 
  is 
  still 
  more 
  developed 
  ; 
  a 
  single 
  row 
  

   of 
  primary 
  tubercles 
  occurs 
  on 
  each 
  side 
  of 
  each 
  interradius 
  ; 
  

   the 
  tubercles 
  are 
  connected 
  by 
  costulate 
  ridges, 
  and 
  the 
  rest 
  of 
  

   the 
  plate 
  is 
  covered 
  \>y 
  very 
  crowded 
  large 
  miliary 
  granules; 
  

   a 
  small 
  row 
  of 
  secondary 
  tubercles 
  may 
  be 
  developed 
  in 
  the 
  

   aboral 
  external 
  corner 
  of 
  each 
  plats. 
  The 
  tubercles 
  are 
  im- 
  

   perforate 
  and 
  crenulate. 
  

  

  Mouth 
  about 
  equal 
  in 
  size 
  to 
  the 
  apical 
  disk, 
  with 
  very 
  

   small 
  branchial 
  slits. 
  

  

  Distribution. 
  Upper 
  Cretaceous 
  of 
  England 
  and 
  Germany 
  ; 
  

   France 
  ? 
  

  

  1. 
  Zewjlopleurus 
  costulatus, 
  sp. 
  nov. 
  (fig. 
  1). 
  

  

  Test 
  small, 
  turban-shaped, 
  depressed, 
  sides 
  tumid. 
  Acti- 
  

   nally 
  concave 
  ; 
  abactinally 
  depressed. 
  Circular 
  at 
  the 
  am- 
  

   bitus, 
  but 
  slightly 
  elongated 
  in 
  the 
  direction 
  of 
  the 
  antero- 
  

   posterior 
  axis. 
  

  

  Apical 
  system 
  rather 
  large 
  and 
  oval. 
  The 
  unpaired 
  basal 
  

   is 
  very 
  narrow. 
  The 
  paired 
  basals 
  are 
  (especially 
  the 
  antero- 
  

   lateral) 
  much 
  larger, 
  and 
  meet 
  within 
  to 
  push 
  the 
  periproct 
  

   posteriorly; 
  all 
  the 
  basals 
  are 
  much 
  pitted 
  and 
  tuberculate; 
  

   but 
  the 
  madreporite 
  is 
  distinct 
  on 
  the 
  right 
  antero-lateral 
  

   basal. 
  The 
  radials 
  are 
  small. 
  

  

  34* 
  

  

  