﻿258 
  Dr. 
  W. 
  T. 
  Caiman 
  on 
  the. 
  

  

  XXIV. 
  — 
  O/i 
  (he 
  Crustacean 
  Genus 
  Sicvonelln, 
  Borradaile. 
  

   By 
  W, 
  T. 
  Calm 
  AN, 
  D.Sc. 
  

  

  (Piiblislied 
  bv 
  permission 
  of 
  tlie 
  Trustees 
  of 
  the 
  British 
  Museum.) 
  

  

  Since 
  the 
  publication 
  of 
  ray 
  recent 
  paper 
  on 
  Ajjhareocans 
  , 
  

   Dr. 
  H. 
  Balss 
  of 
  Munich 
  has 
  kindly 
  drawn 
  my 
  attention 
  

   to 
  the 
  similarity 
  between 
  this 
  genus 
  and 
  Sicyonella, 
  estab- 
  

   lished 
  by 
  Borradaile 
  in 
  1910 
  for 
  a 
  species 
  obtained 
  by 
  

   Prof. 
  J, 
  Stanley 
  Gardiner 
  in 
  the 
  Western 
  Indian 
  Ocean. 
  By 
  

   the 
  kindness 
  of 
  Mr. 
  Borradaile 
  and 
  of 
  Mr. 
  L. 
  Doncaster, 
  

   Supciintendent 
  of 
  the 
  Museum 
  of 
  Zoology, 
  Cambridge, 
  I 
  

   have 
  l)een 
  able 
  to 
  CMamine 
  the 
  type-material 
  of 
  Sicyonella 
  

   maldivensis, 
  with 
  the 
  result 
  that 
  this 
  species 
  proves 
  to 
  be 
  

   identical 
  with 
  my 
  Aphareocaris 
  elegans 
  from 
  Torres 
  Straits. 
  

   The 
  synonymy 
  of 
  the 
  genus 
  must 
  therefore 
  stand 
  as 
  

   follows 
  : 
  — 
  

  

  Genus 
  Sicyonella, 
  Borradaile. 
  

  

  Aphnreus, 
  Paulson, 
  Izslyedovaniya 
  Rakoobraznuikh 
  Krasiiagho 
  Morya, 
  

  

  Kiev, 
  1875, 
  p. 
  117. 
  (Nom. 
  praeocc.) 
  

   Sicyonella, 
  Borradaile, 
  Trans. 
  Linn. 
  Soc, 
  Zo.d. 
  xiii. 
  1910, 
  p. 
  259. 
  

   Aphareucaris, 
  Caiman, 
  Journ. 
  Linn, 
  Soc, 
  Zool. 
  xxxii. 
  1913, 
  p. 
  219. 
  

  

  The 
  discrepancies 
  between 
  Borradaile's 
  description 
  and 
  

   mine 
  are, 
  for 
  the 
  most 
  part, 
  easily 
  explained 
  on 
  comparing 
  

   the 
  type-specimens. 
  The 
  '^ 
  antennal 
  teeth 
  ^^ 
  of 
  the 
  carapace 
  

   in 
  Borradaile's 
  account 
  are 
  really 
  supraorbital 
  in 
  position, 
  

   while 
  his 
  " 
  branchiostegal 
  " 
  tooth 
  is 
  that 
  which 
  I 
  calle(l 
  

   hepatic. 
  The 
  relative 
  length 
  of 
  the 
  third 
  maxillipeds 
  and 
  

   the 
  subdivision 
  of 
  their 
  terminal 
  segments 
  are 
  exactly 
  

   similar 
  in 
  the 
  two 
  iorms. 
  In 
  dealing 
  with 
  the 
  brduchial 
  

   system 
  Borradaile 
  has 
  (1) 
  reckoned 
  as 
  arthrobranchs 
  the 
  

   podobranch 
  of 
  the 
  second 
  maxilliped 
  a^nd 
  the 
  anterior 
  pleuro- 
  

   branchs 
  of 
  the 
  five 
  following 
  somites, 
  (2) 
  assigned 
  to 
  the 
  last 
  

   thoracic 
  somite 
  the 
  posterior 
  |)leurobranch 
  of 
  the 
  somite 
  in 
  

   front, 
  and 
  (3) 
  omitted 
  to 
  notice 
  the 
  vestigial 
  pleurobranchs. 
  

   On 
  all 
  these 
  points 
  error 
  is 
  very 
  eq,sy, 
  and 
  even 
  careful 
  

   examination 
  may 
  leave 
  I'oom 
  for 
  difference 
  of 
  opinion, 
  but 
  

   I 
  still 
  believe 
  tiiat 
  my 
  version 
  of 
  the 
  branchial 
  formula 
  is 
  

   substantially 
  correct. 
  

  

  The 
  most 
  serious 
  obstacle 
  to 
  the 
  identification 
  of 
  the 
  two 
  

   species 
  is 
  that 
  presented 
  by 
  the 
  petasma. 
  As 
  Borradaile's 
  

   figure 
  of 
  this 
  is 
  on 
  a 
  small 
  scale 
  I 
  give 
  an 
  enlarged 
  figure 
  

   taken 
  from 
  one 
  of 
  his 
  specimens, 
  from 
  which 
  it 
  will 
  be 
  seen 
  

   that 
  the 
  organ 
  differs 
  widely 
  from 
  that 
  figured 
  in 
  my 
  former 
  

   paper, 
  especially 
  in 
  the 
  complex 
  branching 
  of 
  the 
  muklle 
  

  

  