﻿134 
  DR. 
  J. 
  W. 
  GREGORY 
  ON 
  [Feb. 
  1897, 
  

  

  diagnoses 
  of 
  the 
  Cystoidea 
  are 
  considered, 
  and 
  it 
  is 
  con- 
  

   tended 
  that 
  they 
  do 
  not 
  enable 
  us 
  to 
  draw 
  any 
  sharp 
  line 
  of 
  

   distinction 
  between 
  the 
  Cystoidea 
  and 
  the 
  Echinoidea. 
  

  

  5. 
  It 
  is 
  shown 
  that 
  the 
  masticatory 
  apparatus 
  of 
  Palceodiscus 
  and 
  

  

  Echinocystis 
  explain 
  the 
  origin 
  of 
  that 
  structure 
  in 
  gnatho- 
  

   stomate 
  echinids. 
  

  

  6. 
  It 
  is 
  suggested 
  that 
  Echinocystis 
  renders 
  probable 
  the 
  homology 
  

  

  of 
  the 
  so-called 
  ' 
  calycinal 
  plates 
  ' 
  of 
  Echinoidea 
  with 
  the 
  

   plates 
  of 
  the 
  valvular 
  pyramid 
  of 
  Cystoidea, 
  and 
  not 
  with 
  

   the 
  calyx-plates. 
  

  

  X. 
  Literature. 
  

  

  1. 
  Bell, 
  F. 
  Jeffrey. 
  ' 
  On 
  the 
  Arrangement 
  and 
  Inter-relations 
  of 
  the 
  Classes 
  

  

  of 
  the 
  Echinodermata,' 
  Ann. 
  Mag. 
  Nat. 
  Hist. 
  ser. 
  6, 
  vol. 
  viii. 
  (1891) 
  

   pp. 
  206-215. 
  

  

  2. 
  Duncan, 
  P. 
  M. 
  'A 
  Eevision 
  of 
  the 
  Genera 
  and 
  Great 
  Groups 
  of 
  the 
  

  

  Echinoidea,' 
  Journ. 
  Linn. 
  Soc, 
  Zool. 
  vol. 
  xxiii. 
  (1890) 
  pp. 
  1-311. 
  

  

  3. 
  Hackel, 
  E. 
  ' 
  Die 
  Ainphorideen 
  und 
  Cystoideen. 
  Beitrage 
  zur 
  Morpho- 
  

  

  logie 
  und 
  Phylogenie 
  der 
  Echinodermen,' 
  Festschr. 
  Gegenbaur, 
  1896, 
  

   vol. 
  i. 
  pp. 
  1-180. 
  pi. 
  i.-v. 
  

  

  4. 
  Jackson, 
  B. 
  T. 
  ' 
  Studies 
  of 
  Palaschinoidea,' 
  Bull. 
  Geol. 
  Soc. 
  Amer. 
  

  

  vol. 
  vii. 
  (1896) 
  pp. 
  171-254, 
  pis. 
  ii.-ix. 
  

  

  5. 
  Loven, 
  S. 
  ' 
  Echinologica,' 
  Bihang 
  k. 
  Svensk. 
  Vet.-Akad. 
  Handl. 
  vol. 
  xviii. 
  

  

  pt. 
  iv. 
  no. 
  1 
  (1892), 
  74 
  pp., 
  12 
  pi. 
  

  

  6. 
  MacBride, 
  E. 
  W. 
  ' 
  The 
  Organogeny 
  of 
  Asterina 
  gibbosa,' 
  Proc. 
  Boy. 
  Soc. 
  

  

  vol. 
  liv. 
  (1894) 
  pp. 
  431-436. 
  

  

  7. 
  Neilmayr, 
  M. 
  ' 
  Morphologische 
  Studien 
  liber 
  fossile 
  Echinodermen,' 
  Sitz. 
  

  

  k. 
  Akad. 
  Wiss. 
  Wien, 
  vol. 
  lxxxiv. 
  pt. 
  i. 
  (1881) 
  pp. 
  143-176, 
  2 
  pi. 
  

  

  8. 
  Poulton, 
  E. 
  B. 
  Presid. 
  Addr. 
  to 
  Sect. 
  D, 
  Brit. 
  Assoc. 
  (L'pool 
  Meeting), 
  

  

  « 
  Nature,' 
  vol. 
  liv. 
  (1896) 
  pp. 
  500-509. 
  

  

  9. 
  Salter. 
  J. 
  W. 
  ' 
  On 
  some 
  New 
  Palaeozoic 
  Starfishes,' 
  Ann. 
  Mag. 
  Nat. 
  

  

  Hist. 
  ser. 
  2, 
  vol. 
  xx. 
  (1857) 
  pp. 
  321-334 
  & 
  pi. 
  ix. 
  

  

  10. 
  Steinmann, 
  G., 
  & 
  Doderlein, 
  L. 
  ' 
  Eleinente 
  der 
  Palaontologie,' 
  pt. 
  i. 
  

  

  (1888) 
  pp. 
  1-336. 
  

  

  11. 
  Thomson, 
  Wyville 
  T. 
  C. 
  ' 
  On 
  a 
  New 
  Palasozoic 
  Group 
  of 
  Echinodermata,' 
  

  

  Edin. 
  New 
  Phil. 
  Journ. 
  vol. 
  xiii. 
  (1861) 
  pp. 
  106-117 
  & 
  pis. 
  iii., 
  iv. 
  

  

  12. 
  Torell, 
  Otto. 
  ' 
  Petrificata 
  Suecana 
  Formationis 
  Cainbricas,' 
  Acta 
  Univ. 
  

  

  Lund. 
  vol. 
  vi. 
  (1869) 
  no. 
  viii. 
  14 
  pp. 
  

  

  13. 
  Worth 
  kn, 
  A. 
  H, 
  & 
  Miller, 
  S. 
  A. 
  ' 
  Descriptions 
  of 
  New 
  Carboniferous 
  

  

  Echinoderms,' 
  Pal. 
  Illinois, 
  vol. 
  vii. 
  (1883) 
  pp. 
  327-338, 
  pi. 
  xxxi. 
  

  

  14. 
  Wright, 
  Th. 
  ' 
  Monograph 
  of 
  the 
  British 
  Fossil 
  Echinodermata 
  of 
  the 
  

  

  Oolitic 
  Formations,' 
  vol. 
  ii. 
  — 
  ' 
  The 
  Asteroidea 
  and 
  Ophiuroidea,' 
  Pal. 
  

   Soc. 
  1863-1880. 
  

  

  15. 
  Zittel, 
  K. 
  ' 
  Handbuch 
  der 
  Palaontologie,' 
  vol. 
  i. 
  pt. 
  iii. 
  (1879). 
  

  

  16. 
  Zittel, 
  K. 
  von. 
  '■ 
  Grundziige 
  der 
  Palaontologie.' 
  (1895.) 
  

  

  EXPLANATION 
  OF 
  PLATE 
  VII. 
  

  

  Fig. 
  1. 
  Pedinothuria 
  cidaroides, 
  sp. 
  n., 
  B.M. 
  34.724.— 
  Figs. 
  1 
  a, 
  b, 
  and 
  c, 
  the 
  

  

  test 
  seen 
  respectively 
  from 
  below, 
  from 
  the 
  side, 
  and 
  from 
  above. 
  

  

  X 
  3 
  diam. 
  

   Fig. 
  1 
  d. 
  Outline. 
  Natural 
  size. 
  

  

  Fig. 
  2. 
  An 
  interambulacrum 
  of 
  the 
  same. 
  X 
  5 
  diam. 
  

   Fig. 
  3 
  a. 
  An 
  ambulacrum 
  of 
  the 
  same. 
  X 
  5 
  diam. 
  Figs. 
  3 
  b, 
  c, 
  and 
  d. 
  Parts 
  

  

  of 
  an 
  ambulacrum, 
  showing 
  arrangement 
  of 
  the 
  plates. 
  

   Fig. 
  4. 
  Echinocystis 
  pomum, 
  Wyv. 
  Th. 
  — 
  A 
  specimen 
  in 
  the 
  British 
  Museum, 
  

  

  from 
  the 
  Leintwardine 
  Flags, 
  showing 
  the 
  aboral 
  surface, 
  with 
  

  

  madreporite 
  and 
  ambulacra. 
  Natural 
  size. 
  

   Fig. 
  5. 
  Palceodiscus 
  ferox, 
  Salt. 
  A 
  specimen 
  in 
  the 
  British 
  Museum, 
  from 
  the 
  

  

  Leintwardine 
  Flags. 
  — 
  Fig. 
  5 
  a, 
  oral 
  side 
  ; 
  5 
  6, 
  the 
  oral 
  armament 
  of 
  

  

  the 
  same 
  specimen, 
  from 
  a 
  wax 
  mould. 
  Natural 
  size. 
  

  

  