﻿A 
  STUDY 
  IX 
  CAECINOLOGT. 
  41 
  

  

  transverse 
  to 
  the 
  long 
  axis 
  o£ 
  the 
  body 
  (with 
  the 
  exception 
  of 
  xiii 
  xv 
  and 
  

   xiv/xv, 
  which 
  arei 
  directly 
  obliquely 
  backwards 
  from 
  the 
  middle 
  line), 
  are 
  of 
  

   no 
  great 
  vertical 
  height, 
  and 
  give 
  off 
  no 
  offset 
  to 
  form 
  a 
  sternal 
  canal. 
  The 
  

   abductor 
  muscle- 
  cavities 
  are 
  of 
  great 
  length 
  and 
  slope 
  backwards, 
  converging 
  

   to 
  a 
  point 
  at 
  the 
  postero-external 
  angle 
  of 
  the 
  thorax 
  on 
  either 
  side. 
  There 
  

   is 
  no 
  mid-ventral 
  longitudinal 
  apodeme 
  and 
  the 
  arthrophragm 
  xiv/xv 
  is 
  

   rudimentary, 
  so 
  there 
  is 
  no 
  trace 
  of 
  a 
  sella 
  turcica. 
  The 
  arrangements 
  of 
  the 
  

   several 
  parts 
  are 
  as 
  widely 
  different 
  as 
  possible 
  from 
  those 
  in 
  Lyreidus 
  or 
  

   any 
  other 
  of 
  the 
  Raninidse. 
  

  

  Though 
  de 
  Haan 
  in 
  the 
  ({notation 
  given 
  above 
  (p. 
  33) 
  draws 
  a 
  contrast 
  

   between 
  the 
  Raninida? 
  and 
  the 
  Dromiacea 
  in 
  the 
  matter 
  of 
  the 
  "apodemata 
  

   cephalica," 
  i.e. 
  the 
  pleural 
  and 
  sternal 
  apodemes 
  of 
  intersegments 
  v/vi— 
  ix/x, 
  

   the 
  Raninidse 
  show 
  more 
  resemblance 
  to 
  the 
  Dromiacea 
  than 
  to 
  the 
  Astacura 
  

   in 
  this 
  region, 
  and 
  the 
  two 
  first-named 
  groups 
  differ 
  largely 
  from 
  the 
  last. 
  

   Passing 
  over 
  the 
  obvious 
  differences 
  due 
  to 
  the 
  presence 
  of 
  a 
  broad 
  and 
  flat 
  

   shield-shaped 
  sternum 
  in 
  the 
  Raninidse, 
  attention 
  may 
  be 
  directed 
  to 
  the 
  

   apodemes 
  entering 
  into 
  the 
  composition 
  of 
  the 
  anterior 
  part 
  of 
  the 
  sternal 
  

   canal. 
  The 
  reader 
  will 
  remember 
  that 
  in 
  the 
  Astacura, 
  of 
  which 
  Sej'hrops 
  

   norvegicus 
  may 
  be 
  taken 
  as 
  a 
  convenient 
  example, 
  the 
  pleural 
  and 
  sternal 
  

   apodemes 
  of 
  the 
  three 
  intersegments 
  in 
  front 
  of 
  ix/x, 
  though 
  some 
  are 
  missing 
  

   and 
  others 
  feebly 
  developed, 
  unite 
  to 
  carry 
  forward 
  the 
  sternal 
  canal 
  towards 
  

   the 
  region 
  of 
  the 
  mouth. 
  In 
  front 
  of 
  them 
  both 
  the 
  sternal 
  and 
  pleural 
  

   apodemes, 
  but 
  particularly 
  the 
  latter, 
  of 
  intersegment 
  v/vi 
  are 
  very 
  largely 
  

   developed, 
  and 
  their 
  expanded 
  internal 
  extremities 
  combine 
  to 
  form 
  a 
  

   stout 
  platform 
  between 
  the 
  suboesophageal 
  ganglion 
  mass 
  and 
  the 
  stomach, 
  

   known 
  to 
  the 
  older 
  carcinologists 
  as 
  the 
  sella 
  turcica 
  anterior. 
  Huxley 
  

   named 
  this 
  platform 
  the 
  cephalic 
  apodeme. 
  In 
  Xotopus 
  and 
  Remind, 
  the 
  

   only 
  two 
  genera 
  of 
  the 
  Raninidoe 
  in 
  which 
  I 
  have 
  been 
  able 
  to 
  study 
  

   these 
  structures 
  in 
  detail, 
  the 
  endosternites 
  and 
  endopleurites 
  of 
  intersegment 
  

   ix/x 
  are 
  normal 
  (figs. 
  9, 
  10, 
  & 
  17), 
  the 
  former 
  standing 
  nearly 
  vertically 
  above 
  

   the 
  plastron 
  and 
  ending 
  above 
  in 
  slightly 
  expanded 
  summits 
  which 
  are 
  

   joined 
  in 
  the 
  usual 
  way 
  by 
  the 
  anterior 
  branches 
  of 
  the 
  corresponding 
  endo- 
  

   pleurites. 
  The 
  endosternites 
  of 
  intersegment 
  viii/ix 
  are 
  small 
  and 
  directed 
  

   backwards 
  to 
  touch 
  the 
  summits 
  of 
  the 
  endosternites 
  behind 
  them. 
  The 
  

   endopleurite 
  of 
  intersegment 
  viii/ix 
  is 
  minute, 
  is 
  not. 
  branched, 
  and 
  converges 
  

   towards 
  the 
  point 
  where 
  endosternites 
  viii/ix 
  and 
  ix/x 
  come 
  into 
  contact. 
  

   Intersegment 
  vii/viii 
  shows 
  only 
  rudimentary 
  endosternites, 
  but 
  its 
  endo- 
  

   pleurites 
  are 
  fairly 
  well 
  developed, 
  exhibiting 
  a 
  very 
  short 
  anterior 
  branch 
  

   and 
  a 
  posterior 
  branch 
  which 
  makes 
  connection 
  with 
  endosternite 
  viii/ix. 
  

   In 
  intersegment 
  vi/vii 
  there 
  is 
  no 
  recognizable 
  endosternite, 
  but 
  the 
  endo- 
  

   pleurite 
  is 
  present 
  in 
  the 
  form 
  of 
  a 
  small 
  incurved 
  lamella. 
  Intersegment 
  

   v/vi 
  is 
  largely 
  membranous, 
  and 
  neither 
  endosternites 
  nor 
  endopleurites 
  can 
  

  

  