﻿316 
  B. 
  ETHER1DGE 
  ON 
  ECHINOTHTTRID.E 
  AND 
  PERISCHOECHINID.E. 
  

  

  in 
  place 
  by 
  a 
  flexible 
  membrane 
  — 
  and 
  as 
  connecting 
  the 
  ordinary- 
  

   forms 
  with 
  Echinothuria, 
  in 
  which 
  the 
  plates 
  slide 
  over 
  one 
  another 
  

   like 
  armour. 
  He 
  remarked 
  that 
  the 
  apical 
  disks 
  vary 
  in 
  each 
  

   genus 
  ; 
  in 
  the 
  palaeozoic 
  genera 
  the 
  ovarian 
  plates 
  have 
  three 
  or 
  

   more 
  and 
  the 
  ocular 
  plates 
  two 
  perforations. 
  The 
  interambulacral 
  

   areas 
  in 
  the 
  palaeozoic 
  genera 
  have 
  invariably 
  more 
  than 
  two 
  rows 
  

   of 
  plates. 
  In 
  Archceocidaris 
  the 
  plates 
  have 
  bevelled 
  edges. 
  The 
  

   chief 
  point 
  of 
  the 
  paper 
  was 
  its 
  indicating 
  that 
  a 
  type 
  supposed 
  to 
  

   have 
  been 
  long 
  extinct 
  is 
  still 
  represented 
  in 
  our 
  seas. 
  

  

  Mr. 
  Seeley 
  observed 
  that 
  the 
  buccal 
  membrane 
  in 
  the 
  recent 
  

   Echinoidea 
  has 
  overlapping 
  plates, 
  so 
  that 
  if 
  the 
  development 
  of 
  the 
  

   plates 
  usually 
  forming 
  the 
  remainder 
  of 
  the 
  test 
  were 
  arrested, 
  forms 
  

   would 
  be 
  obtained 
  approaching 
  those 
  described 
  in 
  the 
  paper. 
  He 
  

   stated 
  that 
  in 
  his 
  opinion 
  both 
  the 
  Echinoderm-type 
  and 
  the 
  Bra- 
  

   chiopod-type 
  have 
  analogies 
  with 
  the 
  Annelids, 
  which 
  are 
  supported 
  

   by 
  a 
  comparison 
  of 
  the 
  multiplied 
  poriform 
  zones 
  of 
  Melonites 
  with 
  

   the 
  perforated 
  shells 
  of 
  Terebratula 
  ; 
  this 
  he 
  thought 
  indicative 
  of 
  

   a 
  far-off 
  affinity 
  between 
  these 
  types. 
  

  

  Mr. 
  H. 
  Woodward 
  stated 
  that 
  the 
  author 
  of 
  the 
  paper 
  had 
  done 
  

   much 
  towards 
  the 
  investigation 
  of 
  the 
  Carboniferous 
  fossils 
  of 
  Scot- 
  

   land. 
  He 
  had 
  detected 
  in 
  the 
  Carboniferous 
  rocks 
  undoubted 
  spi- 
  

   cules 
  of 
  Synapta 
  and 
  Chirodota, 
  showing 
  that 
  the 
  soft-bodied 
  Echi- 
  

   noderms 
  were 
  in 
  existence 
  at 
  the 
  period 
  of 
  their 
  deposition. 
  Mr. 
  

   Woodward 
  further 
  remarked 
  that 
  of 
  the 
  Holothuridae 
  some 
  forms, 
  

   such 
  as 
  Psolus, 
  are 
  protected 
  by 
  calcareous 
  plates 
  having 
  perfect 
  

   freedom 
  of 
  motion. 
  

  

  Mr. 
  Gwyn 
  Jeffreys 
  stated 
  that 
  Oalveria 
  Tiystrix 
  was 
  dredged 
  off 
  

   the 
  Faroe 
  Islands, 
  and 
  subsequently 
  in 
  the 
  Bay 
  of 
  Biscay. 
  He 
  

   remarked 
  that 
  many 
  missing 
  links 
  will 
  probably 
  be 
  found 
  hereafter, 
  

   and 
  that 
  nomenclature 
  will 
  be 
  benefited 
  thereby 
  ; 
  thus, 
  if 
  Echino- 
  

   thuria 
  and 
  Calveria 
  really 
  belong 
  to 
  the 
  same 
  genus, 
  one 
  of 
  these 
  

   names 
  may 
  be 
  discarded. 
  In 
  support 
  of 
  this 
  view 
  he 
  stated 
  that 
  

   the 
  palaeozoic 
  Euomphalus 
  is 
  identical, 
  as 
  regards 
  the 
  characters 
  of 
  

   the 
  shell, 
  with 
  the 
  recent 
  Homalogyra. 
  It 
  is 
  very 
  desirable 
  that 
  

   zoologists 
  and 
  palaeontologists 
  should 
  employ 
  the 
  same 
  names. 
  

  

  