﻿64 
  DR. 
  G. 
  (J. 
  BOURNE 
  ON 
  THE 
  RANINIDjE 
  : 
  

  

  laterally 
  by 
  the 
  smooth 
  and 
  somewhat 
  concave 
  inner 
  surfaces 
  of 
  (he 
  third 
  

   peduncular 
  segment; 
  ventrally 
  by 
  the 
  meri 
  of 
  the 
  third 
  maxillipeds; 
  dorsally 
  

   by 
  the 
  densely 
  setose 
  expods 
  of 
  the 
  first 
  maxillipeds. 
  This 
  may 
  be 
  called 
  the 
  

   inhalant 
  chamber. 
  

  

  The 
  antennules 
  are 
  inserted 
  to 
  the 
  inside 
  of 
  and 
  somewhat 
  above 
  the 
  

   antennas. 
  As 
  shown 
  in 
  figs. 
  34 
  and 
  34 
  a, 
  their 
  basal 
  joints 
  are 
  expanded 
  

   distally 
  into 
  a 
  flabelliform 
  lobe 
  very 
  similar 
  to 
  that 
  of 
  the 
  fourth 
  peduncular 
  

   segment 
  of 
  the 
  antennas 
  and, 
  like 
  the 
  latter, 
  their 
  margins 
  are 
  garnished 
  

   with 
  a 
  fringe 
  of 
  long 
  setas. 
  The 
  slightly 
  concave 
  inner 
  surfaces 
  of 
  these 
  

   flabelliform 
  expansions 
  of 
  the 
  antennules, 
  when 
  opposed 
  in 
  the 
  middle 
  line, 
  

   form 
  a 
  second 
  vertical 
  cleft 
  or 
  passage 
  within 
  the 
  larger 
  passage 
  formed 
  by 
  

   the 
  antennas, 
  and 
  this 
  internal 
  and 
  somewhat 
  dorsal 
  antennulary 
  passage 
  is 
  

   so 
  disposed 
  that 
  its 
  hinder 
  opening 
  coincides 
  with 
  the 
  spout 
  formed 
  by 
  the 
  

   convergence 
  of 
  the 
  exhalant 
  canals 
  of 
  the 
  antennary 
  sternum. 
  The 
  cleft 
  

   between 
  the 
  basal 
  joints 
  of 
  the 
  antennules 
  therefore 
  serves 
  as 
  a 
  conduit 
  for 
  

   the 
  excurrent 
  stream 
  of 
  water. 
  Thus 
  far 
  the 
  apparatus 
  for 
  directing 
  the 
  

   courses 
  of 
  the 
  excurrent 
  and 
  incnrrent 
  respiratory 
  streams 
  differs 
  from 
  that 
  

   of 
  Notopus 
  chiefly 
  in 
  the 
  fact 
  that 
  in 
  Ranina 
  the 
  long 
  tube 
  formed 
  by 
  the 
  

   antennary 
  flagella 
  is 
  absent, 
  but 
  in 
  the 
  latter 
  genus 
  a 
  large 
  part 
  of 
  the 
  

   incurrent 
  stream 
  must 
  find 
  its 
  way 
  into 
  the 
  above-mentioned 
  inhalant 
  

   chamber 
  through 
  the 
  orbital 
  cavities. 
  I 
  have 
  already 
  shown 
  how 
  these 
  

   narrow 
  and 
  elongated 
  cavities 
  are 
  covered 
  in 
  by 
  fringes 
  of 
  setas 
  which 
  meet 
  

   over 
  the 
  retracted 
  eyes 
  and 
  eye-stalks 
  but 
  are 
  pushed 
  aside 
  when 
  the 
  latter 
  

   are 
  extended. 
  Though 
  the 
  orbit 
  appears 
  to 
  be 
  closed 
  below 
  by 
  the 
  crest 
  of 
  

   the 
  third 
  segment 
  of 
  the 
  antennary 
  peduncle, 
  a 
  sufficiently 
  wide 
  space 
  is 
  left 
  

   between 
  this 
  segment 
  and 
  the 
  basal 
  joint 
  of 
  the 
  antennule 
  to 
  allow 
  of 
  the 
  

   free 
  passage 
  of 
  water 
  from 
  the 
  orbit 
  into 
  the 
  inhalant 
  chamber, 
  and 
  much 
  of 
  

   the 
  inhalant 
  current 
  must 
  pass 
  through 
  the 
  orbits. 
  It 
  is 
  evident 
  that 
  when 
  

   the 
  animal 
  is 
  deeply 
  dug 
  in, 
  the 
  broad 
  front 
  of 
  the 
  carapace 
  just 
  breaks 
  the 
  

   surface 
  of 
  the 
  sand 
  ; 
  the 
  tips 
  of 
  the 
  largest 
  frontal 
  spines 
  perhaps 
  project 
  

   very 
  slightly 
  above 
  it. 
  The 
  hairy 
  fringes 
  of 
  the 
  orbits 
  and 
  of 
  the 
  fourth 
  

   joints 
  of 
  the 
  antennas 
  are 
  then 
  just 
  awash 
  between 
  sand 
  and 
  water, 
  and 
  are 
  

   admirably 
  adapted 
  for 
  filtering 
  solid 
  particles 
  from 
  the 
  streams 
  setting- 
  

   inwards 
  through 
  the 
  orbits 
  and 
  between 
  the 
  flabelliform 
  fourth 
  segments 
  of 
  

   the 
  antennas. 
  Water 
  is 
  also 
  admitted 
  into 
  the 
  orbits 
  on 
  either 
  side 
  through 
  

   a 
  considerable 
  cleft 
  lying 
  between 
  the 
  long- 
  and 
  narrow 
  sub-orbital 
  lobe 
  of 
  

   the 
  pterygostome 
  and 
  the 
  innermost 
  of 
  the 
  large 
  frontal 
  spines. 
  These 
  clefts 
  

   are 
  o-uarded 
  by 
  dense 
  hairy 
  fringes. 
  The 
  arrangements 
  by 
  which 
  the 
  

   incurrent 
  stream 
  is 
  directed 
  from 
  the 
  inhalant 
  chamber 
  into 
  the 
  branchial 
  

   chamber 
  by 
  the 
  channel 
  formed 
  by 
  the 
  exopod 
  of 
  the 
  second 
  maxilliped 
  are 
  

   the 
  same 
  in 
  Ranina 
  as 
  in 
  Notojms. 
  

  

  I 
  would 
  not 
  have 
  presumed 
  to 
  give 
  an 
  account 
  unsupported 
  by 
  direct 
  

  

  