﻿A 
  STUDY 
  IX 
  CARCINOLOGY. 
  33 
  

  

  the 
  Raninidae. 
  He 
  says 
  (34, 
  p. 
  136), 
  ''thoracis 
  interior 
  structura 
  offer 
  t 
  

   sellain 
  turcica 
  in 
  nti 
  tan 
  tain 
  in 
  Brachyuiis, 
  atque 
  canalem 
  sternalem 
  uti 
  in 
  

   Macrouris 
  eeterim 
  tantuin 
  invenitur. 
  Apodemata 
  singula 
  tain 
  sterni 
  quani 
  

   epiineroruin 
  ab 
  utraque 
  parte 
  medio 
  thorace 
  junguntur 
  in 
  quoque 
  articulo 
  

   sternali, 
  canalem 
  sternalem 
  constituent 
  vertebrarumque 
  formam 
  plane 
  

   simnlantia. 
  Apodemata 
  cephalica 
  pariter 
  adsunt 
  quinque 
  transversa, 
  ita 
  ut 
  

   Ranina 
  hoc 
  respectu 
  oppositse 
  sunt 
  Dromiis, 
  in 
  quibus 
  apodemata 
  thoracica 
  

   et 
  cephalica 
  separatim 
  versus 
  centrum 
  commune 
  petunt." 
  We 
  have 
  here 
  

   a 
  combination 
  of 
  Macruran 
  and 
  Brachyuran 
  characters 
  which, 
  when 
  the 
  

   ancestry 
  of 
  the 
  Raninidae 
  is 
  in 
  question, 
  deserves 
  close 
  study. 
  As 
  a 
  prelim- 
  

   inary 
  to 
  this 
  part 
  of 
  the 
  subject, 
  T 
  must 
  go 
  fa 
  SO 
  me 
  little 
  detail 
  into 
  the 
  

   structure 
  and 
  morphology 
  of 
  the 
  endophragmal 
  skeleton. 
  It 
  was 
  described 
  

   both 
  for 
  Macrura 
  and 
  Braehyura 
  by 
  Milne 
  Edwards 
  (25), 
  and 
  since 
  his 
  

   day 
  does 
  not 
  seem 
  to 
  have 
  been 
  studied 
  in 
  further 
  detail. 
  We 
  have, 
  sub- 
  

   sequently, 
  the 
  brief 
  but 
  very 
  accurate 
  description 
  of 
  these 
  structures 
  in 
  the 
  

   Crayfish 
  by 
  Huxley 
  (38). 
  His 
  figures, 
  however, 
  are 
  not 
  drawn 
  from 
  a 
  point 
  

   of 
  view 
  that 
  clearly 
  illustrates 
  the 
  structures 
  described, 
  and 
  I 
  shall 
  endeavour, 
  

   with 
  the 
  aid 
  of 
  new 
  figures, 
  to 
  make 
  clear 
  some 
  points 
  that 
  are 
  necessary 
  for 
  

   a 
  detailed 
  comparison 
  with 
  the 
  homologous 
  structures 
  in 
  crabs. 
  Fig. 
  11 
  is 
  a 
  

   ventro-lateral 
  view 
  of 
  the 
  sterna 
  and 
  the 
  endophragmal 
  skeleton 
  of 
  the 
  second 
  

   and 
  third 
  pereiopodal 
  segments 
  of 
  the 
  common 
  Crayfish, 
  seen 
  from 
  the 
  left 
  

   side 
  ; 
  the 
  thorax 
  has 
  been 
  tilted 
  over 
  to 
  the 
  right 
  ; 
  the 
  outlines 
  of 
  the 
  

   articular 
  cavities 
  of 
  the 
  limbs 
  have 
  been 
  thickened 
  to 
  make 
  them 
  more 
  con- 
  

   spicuous. 
  Ventrally 
  we 
  see 
  the 
  keel-shaped 
  sternites, 
  and 
  at 
  the 
  outer 
  side 
  

   of 
  the 
  posterior 
  end 
  of 
  each 
  is 
  a 
  small 
  articular 
  socket, 
  into 
  which 
  fits 
  a 
  

   corresponding 
  knob 
  on 
  the 
  coxa 
  of 
  the 
  appropriate 
  limb. 
  Above 
  are 
  the 
  

   corresponding 
  epimera, 
  separated 
  from 
  one 
  another 
  by 
  a 
  groove 
  which 
  is 
  not 
  

   a 
  suture 
  but 
  a 
  deep 
  infolding 
  of 
  the 
  cuticle, 
  technically 
  known 
  as 
  an 
  apodeme. 
  

   If 
  we 
  follow 
  this 
  groove 
  down 
  below 
  the 
  upper 
  limits 
  of 
  the 
  articular 
  cavities 
  

   of 
  the 
  limbs, 
  we 
  see 
  that 
  it 
  bends 
  forwards, 
  then 
  turns 
  rather 
  abruptly 
  back- 
  

   wards, 
  and 
  seems 
  to 
  end 
  just 
  below 
  a 
  little 
  knob 
  which 
  fits 
  into 
  a 
  corre- 
  

   sponding 
  cavity 
  on 
  the 
  coxa 
  of 
  the 
  appropriate 
  limb. 
  Thus 
  the 
  articular 
  

   knobs, 
  which 
  I 
  shall 
  call 
  strophidia, 
  are 
  borne 
  on 
  prolongations 
  of 
  the 
  anterior 
  

   ends 
  of 
  the 
  pleura, 
  the 
  articular 
  cavities, 
  which 
  I 
  shall 
  call 
  strophingiu, 
  

   on 
  the 
  posterior 
  ends 
  of 
  the 
  sterna 
  *. 
  The 
  line 
  indicating 
  the 
  epimeral 
  

  

  * 
  These 
  small 
  articular 
  knobs 
  and 
  cavities 
  have 
  leen 
  described 
  in 
  some 
  detail, 
  and 
  their 
  

   mechanical 
  action 
  lias 
  been 
  described 
  by 
  Herriclc 
  (37), 
  but 
  though 
  often 
  figured, 
  they 
  seem 
  

   to 
  have 
  been 
  neglected 
  by 
  other 
  authors. 
  As 
  I 
  shall 
  have 
  occasion 
  to 
  refer 
  to 
  them 
  

   frequently 
  and 
  to 
  use 
  them 
  as 
  landmarks, 
  I 
  have 
  found 
  it 
  necessary 
  to 
  give 
  them 
  names 
  and 
  

   call 
  the 
  socket 
  the 
  strophidium, 
  the 
  peg- 
  which 
  fits 
  into 
  it 
  the 
  strophingium. 
  The 
  names 
  are 
  

   derived 
  from 
  the 
  peg 
  (urpocbiyyiov) 
  and 
  socket 
  (aTpo(p(Vi) 
  hinge 
  of 
  a 
  Greek 
  door. 
  For 
  the 
  

   correct 
  formation 
  of 
  the 
  diminutive 
  arpocpevs, 
  arpocpeiSiov, 
  strophidium, 
  I 
  am 
  indebted 
  to 
  

   Mr. 
  Eric 
  Barber 
  of 
  Exeter 
  College. 
  

  

  LINN. 
  JOUItN. 
  — 
  ZOOLOGY, 
  VOL. 
  XXXV. 
  3 
  

  

  