﻿CETISTACEA. 
  307 
  

  

  eyes, 
  are 
  but 
  little 
  produced 
  and 
  rounded, 
  and 
  are 
  received 
  into 
  

   rounded 
  notches 
  in 
  the 
  first 
  segment 
  of 
  the 
  body. 
  The 
  first 
  body- 
  

   segment 
  is 
  longer 
  than 
  the 
  following 
  ; 
  its 
  antero-lateral 
  processes 
  

   narrow, 
  acute, 
  and 
  prolonged 
  forward 
  along 
  the 
  sides 
  of 
  the 
  head 
  

   beyond 
  the 
  eyes 
  ; 
  the 
  postero-lateral 
  angles 
  of 
  all 
  the 
  segments 
  

   (the 
  last 
  excepted) 
  are 
  acute, 
  those 
  of 
  the 
  last 
  body-segment 
  are 
  

   rounded. 
  The 
  postabdomen 
  is 
  divided 
  into 
  two 
  portions, 
  the 
  ante- 
  

   rior 
  of 
  which 
  is 
  minutely 
  punctulated 
  and 
  bears 
  on 
  each 
  side 
  two 
  

   lateral 
  sutures, 
  indicative 
  of 
  coalescent 
  segments 
  ; 
  the 
  posterior 
  

   (or 
  terminal 
  segment) 
  is 
  granulated, 
  subtriangulate, 
  with 
  two 
  low 
  

   rounded 
  elevations 
  on 
  its 
  upper 
  surface 
  ; 
  its 
  distal 
  extremity 
  has 
  a 
  

   rather 
  deep 
  and 
  narrow 
  and 
  somewhat 
  triangulate 
  notch. 
  The 
  

   basal 
  joint 
  of 
  the 
  peduncle 
  of 
  the 
  autennules 
  is 
  much 
  enlarged, 
  

   longer 
  than 
  broad, 
  its 
  distal 
  extremity 
  is 
  excavated, 
  and 
  its 
  distal 
  

   and 
  inferior 
  angle 
  is 
  prolonged 
  into 
  a 
  spine 
  which 
  reaches 
  nearly 
  to 
  

   the 
  extremity 
  of 
  the 
  following 
  joint, 
  which 
  is 
  also 
  dilated, 
  but 
  

   shorter 
  than 
  the 
  preceding 
  ; 
  the 
  very 
  slender 
  flagellum 
  is 
  12-14- 
  

   jointed 
  ; 
  the 
  four 
  exposed 
  joints 
  of 
  the 
  peduncle 
  of 
  the 
  antennae 
  are 
  

   slender, 
  but 
  little 
  more 
  dilated 
  than 
  the 
  joints 
  of 
  the 
  flagellum, 
  

   which 
  are 
  14-16 
  in 
  number. 
  The 
  fourth 
  to 
  sixth 
  joints 
  of 
  the 
  

   ambulatory 
  legs 
  are 
  slender 
  and 
  margined 
  with 
  very 
  short 
  hairs. 
  

   The 
  rami 
  of 
  the 
  uropoda 
  are 
  rather 
  large 
  and 
  dilated, 
  reaching 
  

   beyond 
  the 
  distal 
  end 
  of 
  the 
  terminal 
  segment, 
  and 
  with 
  the 
  

   exterior 
  and 
  distal 
  angles 
  acute 
  and 
  somewhat 
  produced 
  (especially 
  

   in 
  the 
  outer 
  ramus, 
  w^hich 
  is 
  rather 
  the 
  larger) 
  , 
  Colour 
  (in 
  spirit) 
  

   yellowish 
  white, 
  minutely 
  speckled 
  with 
  black. 
  Length 
  nearly 
  

   6 
  lines 
  (12 
  millim.). 
  

  

  Our 
  specimen 
  differs 
  from 
  Milne-Edwards's 
  diagnosis 
  in 
  its 
  punc- 
  

   tulated 
  and 
  granulated 
  postabdomen 
  and 
  the 
  narrower 
  notch 
  of 
  the 
  

   terminal 
  segment 
  ; 
  the 
  first-mentioned 
  is 
  a 
  character 
  which 
  might 
  

   possibly 
  be 
  overlooked 
  on 
  an 
  examination 
  with 
  a 
  lens 
  of 
  low 
  power 
  ; 
  

   nevertheless 
  this 
  variety 
  will 
  perhaps 
  prove 
  a 
  distinct 
  species. 
  

  

  The 
  remarkable 
  structure 
  of 
  the 
  antennules 
  serves, 
  I 
  think, 
  to 
  

   distinguish 
  it 
  generically 
  from 
  the 
  typical 
  species 
  of 
  Dynamene, 
  

   which 
  it 
  resembles 
  in 
  the 
  simply 
  emarginate 
  tail-segment 
  ; 
  but 
  it 
  

   may 
  be 
  found 
  convenient 
  hereafter 
  to 
  separate 
  generically 
  the 
  

   species 
  with 
  a 
  tridentate 
  terminal 
  postabdominal 
  segment 
  from 
  

   those 
  in 
  which 
  this 
  segment 
  is 
  simply 
  notched, 
  as 
  has 
  been 
  done 
  in 
  

   the 
  analogous 
  case 
  of 
  Cymodocea 
  ; 
  the 
  examination, 
  however, 
  of 
  

   further 
  material 
  is 
  required 
  to 
  determine 
  this 
  question. 
  Certain 
  

   species 
  with 
  a 
  tridentate 
  segment 
  closely 
  connect 
  this 
  genus 
  with 
  

   Cymodocea. 
  I 
  may 
  take 
  this 
  opportunity 
  of 
  noting 
  that 
  the 
  Cymo- 
  

   docea 
  granuhta 
  described 
  by 
  me 
  in 
  1876* 
  is 
  probably 
  not 
  specifi- 
  

   cally 
  distinguishable 
  from 
  Cerceis 
  trich'ntata, 
  Milne-Edwards, 
  which 
  

   species, 
  however, 
  is 
  but 
  very 
  briefly 
  characterized. 
  

  

  * 
  Vide 
  'Catalogue 
  New-Zealand 
  Crustacea,' 
  p. 
  114, 
  pi. 
  iii. 
  fig, 
  5 
  (1876). 
  

  

  x2 
  

  

  