﻿No.UM. 
  OBSERVATIONS 
  ON 
  THE 
  ASTACIDJJ:— 
  FAXON. 
  647 
  

  

  CAMBARUS 
  PELLUCIDUS 
  (Tellkampf). 
  

  

  This 
  species 
  has 
  beeu 
  found 
  by 
  Mr. 
  W. 
  P, 
  Hay 
  in 
  Sliiloh 
  Cave, 
  

   Down's 
  Cave, 
  and 
  other 
  caves 
  near 
  Bedford, 
  Lawrence 
  County, 
  Indiana, 
  

   and 
  in 
  a 
  small 
  cave 
  near 
  Paoli, 
  Orange 
  County, 
  Indiana.' 
  The 
  speci- 
  

   mens 
  from 
  these 
  caves 
  belong 
  rather 
  to 
  the 
  form 
  described 
  by 
  Coj)e 
  as 
  

   C 
  inermis 
  (Wyandotte 
  Cave) 
  than 
  to 
  the 
  typical 
  form 
  commonly 
  found 
  

   in 
  the 
  Mammoth 
  Cave 
  of 
  Kentucky. 
  Mr. 
  Hay 
  has 
  shown 
  that 
  these 
  

   specimens 
  are 
  very 
  variable 
  as 
  regards 
  the 
  development 
  of 
  the 
  spines 
  

   of 
  the 
  rostrum 
  and 
  sides 
  of 
  the 
  carapace, 
  and 
  that 
  the 
  reduction 
  of 
  the 
  

   spines 
  is 
  most 
  marked 
  in 
  specimens 
  from 
  the 
  more 
  northerly 
  localities. 
  

   A 
  transition 
  is 
  thus 
  formed 
  through 
  these 
  individuals 
  to 
  the 
  following 
  

   subspecies 
  : 
  

  

  CAMBARUS 
  PELLUCIDUS 
  TESTII 
  Hay. 
  

  

  Camharii8 
  jiellucidus 
  testii 
  Hay, 
  Proc. 
  U. 
  S. 
  Xat. 
  Mus., 
  XVI, 
  1893, 
  p. 
  285, 
  pis. 
  

   XLiv, 
  XLV, 
  figs. 
  2, 
  5, 
  6, 
  10, 
  11, 
  12; 
  Crawfishes 
  of 
  the 
  State 
  of 
  Indiana, 
  

   p. 
  484, 
  fig. 
  4, 
  1896. 
  

  

  In 
  this 
  form, 
  which 
  has 
  been 
  found 
  in 
  Maytield's 
  Cave 
  and 
  Truett's 
  

   Cave, 
  near 
  Bloomington, 
  Indiana 
  (the 
  most 
  northern 
  locality 
  in 
  which 
  

   cave 
  crayfishes 
  were 
  found 
  by 
  ]\rr. 
  Hay), 
  the 
  reduction 
  of 
  the 
  spines 
  is 
  

   carried 
  to 
  the 
  extreme. 
  The 
  lateral 
  spines 
  of 
  the 
  rostrum, 
  the 
  anterior 
  

   spines 
  of 
  the 
  postorbital 
  ridges, 
  and 
  the 
  spines 
  on 
  the 
  sides 
  of 
  the 
  

   carapace 
  are 
  altogether 
  wanting, 
  while 
  the 
  external 
  spine 
  of 
  the 
  second 
  

   antennal 
  segment 
  and 
  the 
  apical 
  spine 
  of 
  the 
  antennal 
  scale 
  are 
  much 
  

   reduced 
  in 
  length. 
  So 
  this 
  form 
  comes 
  to 
  bear 
  a 
  close 
  likeness 
  to 
  

   C. 
  bartonii 
  and 
  suggests 
  the 
  possible 
  derivation 
  of 
  C. 
  pellucidus 
  from 
  

   C. 
  hartonii. 
  It 
  is 
  true 
  that 
  in 
  regard 
  to 
  the 
  structure 
  of 
  the 
  male 
  exter- 
  

   nal 
  organs 
  C 
  pelhicidus 
  is 
  similar 
  to 
  those 
  species 
  of 
  Gambarns 
  that 
  are 
  

   placed 
  in 
  Group 
  I. 
  But, 
  as 
  I 
  pointed 
  out 
  in 
  my 
  "Revision 
  of 
  the 
  Asta- 
  

   cidie" 
  (p. 
  18), 
  this 
  type 
  of 
  the 
  male 
  organ 
  is 
  a 
  very 
  simple 
  and 
  primitive 
  

   one, 
  and 
  might 
  be 
  acquired 
  through 
  an 
  inherent 
  reversionary 
  tendency 
  

   by 
  cave-dwelling 
  species 
  of 
  any 
  of 
  the 
  groups 
  into 
  which 
  the 
  genus 
  

   Cambarus 
  has 
  been 
  divided. 
  The 
  iDresence 
  of 
  hooks 
  upon 
  the 
  fourth 
  

   pair 
  of 
  legs 
  may, 
  in 
  this 
  case, 
  be 
  correlated 
  with 
  the 
  reversion 
  of 
  the 
  

   male 
  appendages 
  to 
  the 
  type 
  of 
  Group 
  1. 
  It 
  will 
  be 
  observed 
  that 
  in 
  

   Form 
  II 
  (the 
  less 
  perfect 
  form 
  of 
  the 
  male) 
  the 
  hooks 
  on 
  the 
  fourth 
  pair 
  

   of 
  legs 
  are 
  more 
  or 
  less 
  abortive 
  not 
  only 
  in 
  C. 
  p. 
  testii 
  but 
  also 
  in 
  the 
  

   typical 
  form 
  of 
  C. 
  pellucidus 
  from 
  the 
  Mammoth 
  Cave. 
  

  

  The 
  difference, 
  pointed 
  out 
  by 
  Hay, 
  between 
  C. 
  p. 
  testii 
  and 
  C. 
  pellu- 
  

   cidus 
  from 
  Shiloh 
  and 
  Wyandotte 
  caves, 
  with 
  regard 
  to 
  the 
  shape 
  of 
  

   the 
  hooks 
  on 
  the 
  third 
  pair 
  of 
  legs, 
  probably 
  results 
  from 
  comparing 
  

   the 
  second 
  form 
  of 
  C. 
  p. 
  testii 
  with 
  the 
  first 
  form 
  of 
  C. 
  pellucidus. 
  

  

  Three 
  types 
  (two 
  males. 
  Form 
  II, 
  one 
  female) 
  of 
  this 
  subspecies 
  are 
  

   in 
  the 
  collection 
  of 
  the 
  United 
  States 
  National 
  Museum 
  (Xo. 
  17702, 
  

   Mayfield's 
  Cave, 
  Indiana, 
  W. 
  P. 
  Hay). 
  

  

  iProc. 
  U. 
  S'. 
  Nat. 
  Miis., 
  XVI, 
  1893, 
  pp. 
  283-285. 
  

  

  