﻿44 
  DR. 
  G. 
  C. 
  BOURNE 
  ON 
  THE 
  RANINIDiE 
  : 
  

  

  of 
  the 
  " 
  epistome." 
  But 
  the 
  French 
  naturalist, 
  usually 
  so 
  exact 
  in 
  the 
  

   definition 
  and 
  use 
  of 
  anatomical 
  terms, 
  goes 
  sadly 
  astray 
  in 
  the 
  application 
  

   of 
  the 
  terms 
  under 
  discussion, 
  and 
  has 
  thus 
  introduced 
  a 
  confusion 
  which 
  

   has 
  persisted 
  in 
  carcinological 
  literature 
  down 
  to 
  the 
  present 
  day. 
  Thus 
  in 
  

   vol. 
  ii. 
  p. 
  170 
  of 
  the 
  ' 
  Histoire 
  Naturelle 
  des 
  Crustaces' 
  we 
  find 
  it 
  stated 
  of 
  

   JJromia, 
  "l'epistome 
  est 
  triangulaire," 
  but 
  clearly 
  the 
  triangular 
  sternal 
  

   element 
  here 
  referred 
  to 
  is 
  the 
  antennulary 
  sternum 
  (see 
  infra, 
  p. 
  50). 
  in 
  

   the 
  same 
  place 
  he 
  says, 
  " 
  le 
  cadre 
  buccal 
  est 
  a 
  pen 
  pres 
  carre," 
  and 
  it 
  is 
  clear 
  

   from 
  an 
  examination 
  in 
  this 
  region 
  in 
  Dramia, 
  that 
  the 
  "cadre 
  buccal 
  " 
  

   is 
  the 
  combined 
  antennary 
  and 
  mandibular 
  sternum, 
  that 
  is, 
  by 
  his 
  own 
  

   definition, 
  the 
  epistome. 
  Again 
  in 
  vol. 
  ii. 
  p. 
  97 
  we 
  find 
  it 
  stated 
  of 
  the 
  

   Oxystomatous 
  crabs, 
  " 
  le 
  cadre 
  buccal 
  est 
  tout-a-fait 
  triangulaire, 
  " 
  and 
  on 
  

   p. 
  102 
  of 
  the 
  Calappidje, 
  "il 
  n'y 
  a 
  point 
  d'epistome 
  distinct." 
  But 
  a 
  study 
  

   of 
  these 
  crabs 
  shows 
  that 
  the 
  triangular 
  "cadre 
  buccal 
  " 
  is 
  chiefly 
  made 
  up 
  

   of 
  the 
  antennary 
  sternum, 
  i.e., 
  it 
  is 
  the 
  epistome, 
  which 
  is 
  said 
  to 
  be 
  absent 
  ! 
  

   Among 
  more 
  recent 
  authors, 
  Oalman 
  (23, 
  p. 
  257) 
  writes: 
  "the 
  antennal 
  

   sternum 
  is 
  mainly 
  represented 
  by 
  the 
  epistome, 
  a 
  plate 
  of 
  varying 
  shape 
  

   lying 
  between 
  the 
  labrum 
  and 
  the 
  bases 
  of 
  the 
  antennae," 
  and 
  further 
  on 
  

  

  *'the 
  buccal 
  frame 
  is 
  more 
  or 
  less 
  distinctly 
  delimited 
  by 
  the 
  epistome 
  

  

  itself 
  or 
  by 
  a 
  transverse 
  ridge 
  which 
  divides 
  the 
  epistome 
  into 
  two 
  parts, 
  

   the 
  epistome 
  proper 
  and 
  the 
  endostome 
  or 
  palate." 
  He 
  does 
  not, 
  with 
  

   Huxlev, 
  recognise 
  the 
  inclusion 
  of 
  the 
  mandibular 
  sternum, 
  but 
  there 
  can 
  be 
  

   no 
  doubt 
  that 
  Caiman 
  identifies 
  the 
  greater 
  part 
  of 
  the 
  " 
  epistome 
  " 
  with 
  the 
  

   antennary 
  sternum. 
  A 
  little 
  further 
  on 
  the 
  same 
  author 
  makes 
  the 
  following 
  

   statement 
  : 
  "In 
  all 
  the 
  Brachyura 
  the 
  rostrum 
  or 
  frontal 
  plates 
  ends 
  down- 
  

   wards 
  in 
  the 
  middle 
  line 
  a 
  process 
  which 
  unites 
  in 
  front 
  of 
  the 
  ophthalmic 
  

   and 
  antennular 
  sterna 
  with 
  the 
  epistome 
  and 
  separates 
  from 
  one 
  another 
  

   the 
  basal 
  segments 
  of 
  the 
  antennules." 
  This 
  represents 
  accurately 
  enough 
  

   the 
  prevailing 
  opinion 
  on 
  the 
  subject, 
  and 
  indicates 
  quite 
  clearly 
  that 
  the 
  

   antennulary 
  sternum 
  is 
  not 
  to 
  be 
  regarded 
  as 
  a 
  component 
  part 
  of 
  the 
  

   "epistome/' 
  But, 
  whilst 
  this 
  part 
  of 
  the 
  statement 
  is 
  accurate, 
  the 
  re- 
  

   maining" 
  part 
  is 
  most 
  inaccurate, 
  for 
  an 
  examination 
  of 
  a 
  large 
  number 
  of 
  

   crabs 
  belonging 
  to 
  diverse 
  families 
  shows 
  that, 
  with 
  very 
  few 
  exceptions, 
  the 
  

   downward 
  process 
  of 
  the 
  front 
  or 
  rostrum 
  does 
  not 
  unite 
  with 
  the 
  antennary 
  

   sternum, 
  that 
  is 
  with 
  the 
  epistome, 
  but 
  with 
  the 
  antennulary 
  sternum. 
  The 
  

   fact 
  is 
  so 
  obvious 
  that 
  it 
  is 
  difficult 
  to 
  understand 
  how 
  the 
  error 
  originated, 
  

   the 
  more 
  so 
  because 
  Milne 
  Edwards, 
  however 
  obscure 
  he 
  may 
  have 
  been 
  on 
  

   the 
  subject 
  of 
  the 
  epistome, 
  is 
  quite 
  definite 
  and 
  exact 
  on 
  this 
  point. 
  " 
  Le 
  

   front 
  se 
  prolonge 
  au-dessus 
  de 
  l'anneau 
  qui 
  porte 
  les 
  yeux. 
  Dans 
  le 
  jeune 
  

   age, 
  cet 
  anneau 
  reste 
  a 
  decouvert 
  anterieurement, 
  et 
  les 
  yeux 
  ne 
  sont 
  pas 
  

   loges 
  dans 
  des 
  cavites 
  orbitaires 
  completes 
  ; 
  mais, 
  plus 
  tard, 
  la 
  partie 
  

   inferieure 
  du 
  front 
  se 
  reunit, 
  sur 
  la 
  ligne 
  mediane, 
  a 
  une 
  prolongement 
  de 
  

  

  