﻿266 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol. 
  44. 
  

  

  as 
  follows: 
  First 
  exopod, 
  III 
  — 
  0, 
  IV 
  — 
  5, 
  V 
  — 
  2; 
  second 
  cndopod, 
  

   III— 
  1, 
  IV— 
  1, 
  IV— 
  3. 
  Second 
  exopod, 
  II— 
  0, 
  IV— 
  1, 
  IV— 
  4; 
  

   third 
  endopod, 
  II— 
  1, 
  III— 
  1, 
  VI— 
  4; 
  third 
  exopod, 
  I— 
  0, 
  I— 
  1, 
  

   IV— 
  3; 
  fourth 
  endopod, 
  0—1, 
  III— 
  0, 
  IV— 
  4. 
  Fourth 
  exopod, 
  I— 
  0, 
  

   V 
  — 
  0, 
  VI 
  — 
  2. 
  Fifth 
  legs 
  uniramose, 
  lamellar, 
  two-jointed, 
  the 
  basal 
  

   joint 
  with 
  a 
  single 
  seta 
  on 
  the 
  outer 
  side 
  and 
  expanded 
  on 
  the 
  inner 
  

   side 
  into 
  a 
  broad 
  lamina 
  terminated 
  by 
  four 
  setae; 
  distal 
  joint 
  narrow 
  

   oblong, 
  terminated 
  by 
  four 
  slender 
  setse. 
  

  

  No 
  females 
  were 
  found 
  with 
  attached 
  egg-cases, 
  but 
  the 
  external 
  

   opening 
  of 
  the 
  oviducts 
  was 
  single, 
  showing 
  that 
  there 
  can 
  be 
  but 
  a 
  

   single 
  egg-case. 
  

  

  Total 
  length, 
  exclusive 
  of 
  setae, 
  0.8 
  mm. 
  Greatest 
  width 
  (first 
  

   free 
  thorax 
  segment), 
  0.175 
  m,m. 
  Length 
  of 
  anal 
  setse, 
  0.425 
  mm. 
  

  

  Color 
  a 
  uniform 
  transparent 
  white, 
  the 
  ovaries 
  and 
  digestive 
  tube 
  

   somewhat 
  darker 
  in 
  coloi'. 
  

  

  Male. 
  — 
  General 
  form 
  similar 
  to 
  that 
  of 
  the 
  female 
  with 
  the 
  follow- 
  

   ing 
  differences: 
  Cephalon 
  proportionally 
  much 
  longer 
  and 
  wider 
  at 
  

   its 
  posterior 
  end 
  than 
  any 
  of 
  the 
  succeeding 
  portions 
  of 
  the 
  body. 
  

   First 
  free 
  segment 
  with 
  a 
  conspicuous 
  indentation 
  on 
  either 
  side 
  

   near 
  the 
  anterior 
  margin; 
  anal 
  setae 
  only 
  one-third 
  the 
  length 
  of 
  the 
  

   body. 
  

  

  First 
  antennae 
  distinctly 
  hinged, 
  the 
  second 
  and 
  fourth 
  joints 
  

   meeting 
  on 
  the 
  anterior 
  margin, 
  both 
  of 
  them 
  heavily 
  armed 
  with 
  

   setae 
  and 
  with 
  a 
  single 
  large 
  aesthetask 
  at 
  the 
  distal 
  end 
  of 
  the 
  fourth 
  

   joint; 
  third 
  jomt 
  seen 
  only 
  on 
  the 
  posterior 
  margin 
  and 
  unarmed. 
  

   Mouth 
  parts 
  and 
  first 
  legs 
  like 
  those 
  of 
  the 
  female; 
  second, 
  third, 
  and 
  

   fourth 
  legs 
  with 
  the 
  endopods 
  less 
  distinctly 
  segmented, 
  the 
  last 
  

   two 
  joints 
  especially 
  being 
  often 
  more 
  or 
  less 
  fused, 
  but 
  with 
  the 
  

   number 
  of 
  setae 
  and 
  spines 
  practically 
  the 
  same 
  and 
  similarly 
  

   arranged; 
  fifth 
  legs 
  much 
  smaller 
  than 
  m 
  the 
  female, 
  reduced 
  to 
  a 
  

   simple 
  tiny 
  process 
  tipped 
  with 
  two 
  short 
  setae. 
  

  

  Total 
  length, 
  0.88 
  mm. 
  Greatest 
  width 
  (posterior 
  margin 
  of 
  the 
  

   cephalon), 
  0.17 
  mm. 
  Anal 
  setae, 
  0.33 
  mm. 
  long. 
  

  

  Color 
  like 
  that 
  of 
  the 
  female. 
  

  

  {jamaicensis, 
  a 
  native 
  of 
  Jamaica.) 
  

  

  These 
  tiny 
  copepods 
  are 
  common 
  on 
  the 
  gills 
  of 
  the 
  white 
  land 
  crab 
  

   of 
  Jamaica, 
  nearly 
  every 
  specimen 
  examined 
  bemg 
  infested 
  with 
  them. 
  

   They 
  cling 
  to 
  the 
  gill 
  filaments 
  with 
  their 
  second 
  anteimae 
  and 
  maxil- 
  

   lipeds, 
  but 
  are 
  dislodged 
  much 
  more 
  easily 
  than 
  the 
  Ergasilidae 
  or 
  

   other 
  small 
  copepods 
  that 
  fasten 
  similarly 
  on 
  the 
  gill 
  filaments 
  of 
  

   fishes. 
  As 
  many 
  as 
  25 
  or 
  30 
  may 
  sometimes 
  be 
  obtained 
  from 
  the 
  

   gills 
  of 
  a 
  single 
  crab. 
  In 
  connection 
  mth 
  their 
  parasitism 
  upon 
  this 
  

   host 
  several 
  extremely 
  interesting 
  questions 
  arise 
  which 
  can 
  not 
  be 
  

   finally 
  settled 
  without 
  considerable 
  further 
  observation. 
  But 
  there 
  

  

  