﻿428 
  Kev. 
  T. 
  Hincks 
  on 
  the 
  

  

  In 
  one 
  of 
  his 
  papers 
  * 
  Jullien 
  has 
  stated 
  that 
  he 
  had 
  seen 
  a 
  

   colony 
  of 
  Scrupocellaria 
  scabra 
  from 
  Greenland 
  on 
  which 
  not 
  

   a 
  single 
  vibraculum 
  was 
  present, 
  but 
  the 
  avicularia 
  on 
  the 
  

   front 
  surface 
  were 
  strongly 
  developed. 
  In 
  the 
  case 
  of 
  the 
  

   St.- 
  Lawrence 
  form 
  the 
  latter 
  also 
  have 
  disappeared. 
  It 
  may 
  

   be 
  noted 
  that 
  in 
  this 
  species, 
  in 
  which 
  the 
  vibracula 
  are 
  of 
  

   such 
  uncertain 
  occurrence, 
  these 
  appendages 
  are 
  of 
  most 
  rudi- 
  

   mentary 
  structure, 
  and 
  a 
  very 
  slight 
  modification 
  of 
  the 
  avicu- 
  

   larium. 
  The 
  scutum 
  in 
  the 
  present 
  form 
  is 
  very 
  highly 
  

   developed 
  and 
  of 
  exceptionally 
  large 
  size, 
  in 
  some 
  cases 
  

   almost 
  completely 
  concealing 
  the 
  ocecium. 
  

  

  The 
  normal 
  form 
  of 
  8. 
  scabra 
  occurs 
  in 
  the 
  St. 
  Lawrence. 
  

  

  Range. 
  Gaspe 
  Bay, 
  St. 
  Lawrence 
  ; 
  Greenland. 
  

  

  Family 
  Escharidse 
  (part.), 
  Smitt. 
  

  

  Porella, 
  Gray. 
  

  

  Porella 
  concinna, 
  Busk. 
  (PI. 
  XXI. 
  fig. 
  4.) 
  

  

  This 
  is 
  one 
  of 
  the 
  most 
  abundant 
  species 
  in 
  the 
  St. 
  

   Lawrence, 
  and 
  exhibits 
  a 
  large 
  amount 
  of 
  variation. 
  One 
  of 
  

   the 
  prettiest 
  varieties 
  is 
  represented 
  in 
  figure 
  4. 
  The 
  remark- 
  

   able 
  diversity 
  in 
  the 
  condition 
  of 
  the 
  cell-wall, 
  which 
  is 
  such 
  

   a 
  marked 
  characteristic 
  of 
  the 
  Polyzoa, 
  receives 
  ample 
  illus- 
  

   tration 
  in 
  this 
  species 
  ; 
  commonly 
  the 
  surface 
  is 
  uniformly 
  

   granulous, 
  and 
  a 
  line 
  of 
  rather 
  large 
  punctures 
  runs 
  round 
  

   the 
  margin 
  of 
  the 
  cells. 
  In 
  other 
  cases 
  the 
  surface 
  is 
  perfectly 
  

   smooth 
  and 
  white 
  and 
  the 
  margin 
  of 
  the 
  cell 
  is 
  strongly 
  sinu- 
  

   ated 
  and 
  punctured. 
  

  

  This 
  very 
  marked 
  form 
  is 
  the 
  Lepralia 
  Belli 
  of 
  Dawson, 
  

   and 
  is 
  extremely 
  abundant 
  in 
  the 
  St. 
  Lawrence. 
  In 
  yet 
  

   another 
  (which 
  occurs 
  in 
  the 
  North 
  Pacific) 
  the 
  whole 
  surface 
  

   of 
  the 
  cell, 
  except 
  the 
  suboral 
  umbo, 
  is 
  covered 
  with 
  rather 
  

   large 
  punctures 
  ; 
  in 
  another 
  even 
  the 
  marginal 
  punctures 
  are 
  

   obliterated 
  by 
  the 
  calcification 
  or 
  altogether 
  absent. 
  Such 
  

   facts, 
  and 
  they 
  might 
  be 
  multiplied 
  to 
  almost 
  any 
  extent, 
  

   suggest 
  a 
  serious 
  objection 
  to 
  Dr. 
  Jullien's 
  proposal 
  to 
  employ 
  

   the 
  characters 
  of 
  the 
  front 
  wall 
  for 
  classificatory 
  purposes 
  — 
  

   to 
  make 
  them 
  primary 
  tests 
  of 
  natural 
  affinity. 
  The 
  practical 
  

   difficulties 
  in 
  the 
  way 
  would 
  seem 
  to 
  be 
  great 
  ; 
  but 
  I 
  am 
  

   by 
  no 
  means 
  disposed 
  to 
  deny 
  that 
  in 
  many 
  cases 
  they 
  may 
  

   yield 
  valuable 
  help 
  to 
  the 
  systematise 
  

  

  In 
  the 
  cells 
  on 
  the 
  growing 
  edge 
  of 
  the 
  colony 
  and 
  in 
  the 
  

   neighbouring 
  region 
  the 
  avicularium 
  is 
  borne 
  on 
  the 
  summit 
  

  

  * 
  " 
  Dragages 
  da 
  Travailteur. 
  Bryozoaires 
  : 
  especes 
  draguees 
  daiif 
  

   1'ocean 
  Atlantique 
  en 
  1881," 
  Bull, 
  de 
  la 
  Soc. 
  Zool. 
  deFrance, 
  t. 
  vii. 
  (188:?). 
  

  

  