﻿COOKE 
  : 
  ON 
  GENEKIC 
  POSITION 
  OF 
  NOIiTIIIA. 
  235 
  

  

  of 
  the 
  so-called 
  Cape 
  Cominellcc, 
  elongata, 
  Dunk., 
  and 
  tigrina, 
  Kien. 
  

   It 
  has 
  further 
  the 
  characteristic 
  that 
  the 
  interior 
  cusp 
  of 
  the 
  

   lateral 
  is 
  serrated 
  all 
  along 
  the 
  inner 
  edge. 
  

  

  Group 
  Ij.. 
  — 
  Khachidian 
  tooth 
  tricuspid 
  on 
  a 
  rather 
  narrow 
  hase, 
  

   base 
  strongly 
  arched 
  below, 
  and 
  more 
  or 
  less 
  prolonged 
  into 
  wings 
  ; 
  

   laterals 
  bicuspid, 
  simple, 
  outer 
  cusp 
  the 
  longer 
  and 
  narrower. 
  

   To 
  this 
  type 
  belong 
  the 
  Magellanic 
  species 
  antarctica, 
  Smith, 
  fuscata, 
  

   Urug., 
  fuscata, 
  Brug., 
  var. 
  curta, 
  Prest., 
  and 
  innocens. 
  Smith. 
  There 
  

   is 
  strong 
  reason 
  to 
  suspect 
  that 
  Preston's 
  var. 
  curta 
  oi 
  fuscata, 
  Brug.,' 
  

   is 
  a 
  distinct 
  species 
  from 
  fuscata 
  ; 
  the 
  three 
  rhachidian 
  cusps 
  are 
  

   differently 
  shaped, 
  and 
  set 
  at 
  a 
  different 
  angle.- 
  It 
  appears 
  from 
  

   von 
  Max'tens' 
  description^ 
  of 
  the 
  radula 
  of 
  his 
  E. 
  clilorotica 
  that 
  that 
  

   species 
  also 
  belongs 
  to 
  this 
  group, 
  and 
  here 
  too 
  must 
  be 
  classified 
  the 
  

   West 
  American 
  E. 
  dira, 
  Becve, 
  which 
  possesses 
  a 
  tricuspid 
  rhachidian, 
  

   set 
  on 
  a 
  base 
  which 
  is 
  rounded 
  above, 
  and 
  deeply 
  arched 
  below, 
  sides 
  

   produced 
  into 
  wings 
  ; 
  laterals 
  bicuspid,^ 
  simple. 
  

  

  A 
  comparison 
  of 
  the 
  radulae 
  of 
  Group 
  4 
  with 
  those 
  of 
  the 
  ComineUce 
  

   of 
  New 
  Zealand 
  {antea, 
  p. 
  228) 
  will 
  suggest 
  the 
  conclusion 
  that 
  the 
  

   Magellanic 
  Euthrias 
  are 
  in 
  fact 
  Cominellas, 
  and 
  should 
  be 
  classified 
  

   as 
  such. 
  It 
  is 
  noticeable 
  that, 
  in 
  the 
  Falklands 
  at 
  least, 
  " 
  Euthria" 
  

   occurs 
  on 
  muddy 
  shores, 
  and 
  Mr. 
  Iredale 
  tells 
  me 
  that 
  in 
  New 
  

   Zealand 
  and 
  on 
  Norfolk 
  Island 
  Cominella 
  is 
  always 
  found 
  associated 
  

   Avith 
  mud. 
  

  

  EXPLANATION 
  OF 
  FIGUEES. 
  

  

  1. 
  Euthria 
  cornea, 
  L. 
  : 
  Naples. 
  

  

  2. 
  ,, 
  Zi?iea, 
  Mart. 
  : 
  New 
  Zealand. 
  

  

  3. 
  ,, 
  /e;Tca, 
  Reeve 
  : 
  Japan. 
  

  

  4. 
  ,, 
  littorinoides, 
  'Reeve: 
  Auckland 
  Island, 
  New 
  Zealand. 
  

  

  5. 
  ,, 
  vittata, 
  Quoy 
  : 
  New 
  Zealand. 
  

  

  6. 
  ,, 
  cZarA;ei, 
  T. 
  -Woods 
  : 
  South 
  Australia. 
  

  

  7. 
  ,, 
  gwefce^ii, 
  Smith 
  : 
  South 
  Africa. 
  

  

  8. 
  ,, 
  antarctica, 
  Smith 
  : 
  Cape 
  Horn. 
  

  

  9. 
  ,, 
  fuscata, 
  Brug. 
  : 
  Chile. 
  

  

  10. 
  ,, 
  /itscrt 
  to, 
  Brug., 
  var. 
  cwrto, 
  Prest. 
  : 
  Falkland 
  Islands. 
  

  

  11. 
  ,, 
  dira, 
  Reeve 
  : 
  Vancouver. 
  

  

  THE 
  GENERIC 
  POSITION 
  OF 
  THE 
  GENUS 
  NOBTHIA, 
  GRAY. 
  

  

  By 
  the 
  Rev. 
  A. 
  H. 
  Cooke, 
  Sc.D., 
  F.Z.S. 
  

  

  Bead 
  13th 
  April, 
  1917. 
  

  

  The 
  genus 
  Northia 
  was 
  constituted 
  by 
  Gray 
  (Proc. 
  Zool. 
  See. 
  Lond., 
  

   1847, 
  p. 
  140) 
  for 
  his 
  JVassa 
  northim. 
  In 
  his 
  " 
  List 
  of 
  the 
  Genera 
  of 
  

  

  ^ 
  Ann. 
  Mag. 
  Nat. 
  Hist., 
  ser. 
  vill, 
  vol. 
  xi, 
  1913, 
  p. 
  218 
  (not 
  figured). 
  

  

  - 
  There 
  can 
  be 
  no 
  doubt 
  of 
  the 
  identifieation, 
  as 
  Gwatkin 
  had 
  his 
  specimens 
  

  

  from 
  Preston. 
  

   ^ 
  " 
  Mittelplatte 
  der 
  Radula 
  mit 
  3 
  Zahnen, 
  wovon 
  der 
  niittlere 
  langer, 
  Seiten- 
  

  

  platte 
  mit 
  zwei 
  starken 
  einwarts 
  gekriimmten 
  Zahnen, 
  wovon 
  der 
  aussere 
  

  

  langer, 
  aber 
  schmiiler 
  " 
  : 
  Sitzungsb. 
  Naturf. 
  Fr. 
  Berlin, 
  1878, 
  p. 
  22. 
  

   * 
  One 
  specimen 
  shows 
  the 
  remarkable 
  variation 
  of 
  a 
  normal 
  bicuspid 
  lateral 
  on 
  

  

  one 
  side, 
  while 
  the 
  inner 
  tooth 
  of 
  the 
  lateral 
  on 
  the 
  other 
  side 
  is 
  in 
  every 
  

  

  case 
  deeply 
  cloven, 
  making 
  the 
  tooth 
  tricuspid. 
  

  

  VOL. 
  XII. 
  — 
  AUGUST, 
  1917. 
  17 
  

  

  