﻿248 
  PROCEEDIXaS 
  of 
  the 
  national 
  museum. 
  vol.44. 
  

  

  separation 
  of 
  tho 
  two 
  leg-bearing: 
  thorax 
  segments. 
  In 
  most 
  other 
  

   species 
  these 
  are 
  more 
  or 
  h^ss 
  fused 
  with 
  the 
  three 
  following 
  segments 
  

   to 
  form 
  the 
  so-called 
  " 
  body" 
  of 
  the 
  copepod. 
  Here 
  they 
  are 
  entirely 
  

   separated 
  and 
  the 
  species 
  may 
  be 
  recognized 
  by 
  this 
  separation 
  at 
  a 
  

   glance. 
  

  

  If 
  any 
  essential 
  differences 
  could 
  be 
  found 
  in 
  the 
  appendages, 
  such 
  

   a 
  separation 
  would 
  warrant 
  the 
  establishment 
  of 
  a 
  new 
  ge*nus, 
  but 
  as 
  

   the 
  appendages 
  are 
  in 
  every 
  way 
  similar 
  to 
  those 
  in 
  all 
  HatscheJcia 
  

   species, 
  it 
  seems 
  best 
  to 
  locate 
  this 
  new 
  form 
  in 
  that 
  genus. 
  Another 
  

   difference 
  is 
  tho 
  long 
  distance 
  between 
  the 
  mouth 
  j^arts 
  and 
  tho 
  first 
  

   swimming 
  legs. 
  Usually 
  these 
  first 
  legs 
  are 
  so 
  close 
  to 
  tho 
  maxillipeds 
  

   that 
  they 
  are 
  often 
  partially 
  concealed 
  beneath 
  the 
  latter. 
  Here 
  there 
  

   is 
  a 
  wide 
  interval 
  between 
  the 
  two. 
  

  

  The 
  species 
  is 
  quite 
  common, 
  nearly 
  every 
  fish 
  yielding 
  specimens, 
  

   but 
  it 
  is 
  not 
  at 
  all 
  numerous, 
  as 
  only 
  two 
  or 
  three 
  specimens 
  could 
  be 
  

   found 
  on 
  any 
  one 
  fish, 
  and 
  the 
  most 
  careful 
  search 
  of 
  many 
  fish 
  failed 
  

   to 
  reveal 
  a 
  single 
  male. 
  In 
  the 
  separation 
  of 
  the 
  two 
  leg-bearing 
  

   segments 
  and 
  in 
  the 
  relative 
  position 
  of 
  the 
  mouth 
  parts 
  and 
  first 
  legs 
  

   Hatschekia 
  (Clavella) 
  tenuis 
  Heller 
  closely 
  resembles 
  the 
  present 
  

   species, 
  but 
  the 
  two 
  differ 
  radically 
  in 
  the 
  relative 
  proportions 
  of 
  

   the 
  different 
  parts 
  of 
  the 
  body, 
  as 
  well 
  as 
  in 
  the 
  size 
  and 
  structure 
  

   of 
  the 
  antennae 
  and 
  mouth 
  parts. 
  

  

  HATSCHEKIA 
  IRIDESCENS, 
  new 
  species. 
  

   Plate 
  41, 
  figs. 
  216-221; 
  plate 
  44, 
  fig. 
  247; 
  plate 
  45. 
  

  

  Host 
  and 
  record 
  of 
  specimens. 
  — 
  About 
  50 
  females 
  and 
  2 
  males 
  

   were 
  obtained 
  from 
  the 
  gills 
  of 
  a 
  porcupine 
  fish, 
  Diodon 
  hi/strix, 
  

   15 
  inches 
  in 
  length. 
  The 
  females 
  were 
  attached 
  between 
  the 
  gill 
  

   filaments, 
  the 
  great 
  majority 
  of 
  them 
  with 
  their 
  heads 
  toward 
  the 
  

   base 
  of 
  the 
  filaments, 
  and 
  all 
  with 
  their 
  bodies 
  parallel 
  with 
  the 
  fila- 
  

   ments. 
  The 
  males 
  were 
  attached 
  to 
  the 
  tips 
  of 
  the 
  filaments, 
  and 
  

   not 
  at 
  air 
  securely. 
  

  

  Type-specimen. 
  — 
  A 
  female. 
  Cat. 
  No. 
  43550, 
  U.S.N.M. 
  Paratypes, 
  

   Cat. 
  No. 
  42325, 
  U.S.N.M. 
  

  

  Female. 
  — 
  Body 
  short 
  and 
  of 
  medium 
  width; 
  carapace 
  very 
  large, 
  

   one-third 
  of 
  the 
  entire 
  length, 
  semielliptical, 
  three-fifths 
  wider 
  than 
  

   long, 
  the 
  lateral 
  and 
  posterior 
  margins 
  a 
  nearly 
  even 
  curve, 
  the 
  

   anterior 
  margin 
  four-lobed, 
  a 
  narrow 
  lobe 
  on 
  either 
  side 
  of 
  the 
  median 
  

   line, 
  with 
  a 
  much 
  wider 
  one 
  outside 
  of 
  it 
  extending 
  to 
  the 
  lateral 
  

   margin. 
  Dorsal 
  surface 
  with 
  a 
  median 
  longitudinal 
  keel 
  extending 
  

   its 
  entire 
  length, 
  the 
  strong 
  muscles 
  operating 
  the 
  second 
  antennae 
  

   and 
  mouth 
  parts 
  attached 
  to 
  it 
  and 
  showing 
  as 
  diagonal 
  lines 
  on 
  either 
  

   side 
  of 
  it. 
  

  

  Fused 
  thorax 
  elongate-ovate, 
  one-half 
  longer 
  than 
  wide, 
  a 
  little 
  

   narrower 
  than 
  the 
  carapace, 
  with 
  only 
  the 
  anterior 
  segments 
  indicated 
  

   by 
  lateral 
  indentations. 
  The 
  two 
  leg-bearing 
  segments 
  fused 
  with 
  

  

  