﻿NO. 
  1136. 
  OBSERVATIONS 
  ON 
  THE 
  ASTACIDM— 
  FAXON. 
  689 
  

  

  tubercles, 
  hands 
  swollen, 
  rounded 
  above 
  and 
  below, 
  slig'htly 
  tubercu- 
  

   liite 
  on 
  their 
  upper 
  margin, 
  and 
  scarcely 
  punctate. 
  The 
  anterior 
  proc- 
  

   ess 
  of 
  the 
  epistome 
  is 
  shaped 
  as 
  in 
  Astacus 
  astacus, 
  but 
  it 
  is 
  separated 
  

   from 
  the 
  body 
  of 
  the 
  epistome 
  by 
  a 
  transverse 
  furrow. 
  Length 
  about 
  

   three 
  inches. 
  It 
  would 
  seem 
  from 
  Milne-Edwards's 
  diagnosis 
  and 
  from 
  

   the 
  same 
  author's 
  description 
  and 
  figure 
  of 
  Astacus 
  australasiensis 
  

   that, 
  whatever 
  Astacus 
  chilensis 
  may 
  prove 
  to 
  be, 
  it 
  is 
  neither 
  of 
  the 
  

   two 
  Chilean 
  crayfishes 
  described 
  in 
  this 
  paper. 
  In 
  1849, 
  Mcolet^ 
  

   described 
  and 
  figured 
  as 
  Astacus 
  chilensis 
  Milne-Edwards, 
  a 
  species 
  of 
  

   crayfish 
  found 
  "in 
  the 
  rivers 
  of 
  Chile" 
  — 
  a 
  species 
  manifestly 
  distinct 
  

   from 
  Milne-Edwards's. 
  For, 
  not 
  to 
  mention 
  other 
  peculiarities, 
  the 
  

   carpus 
  is 
  described 
  and 
  figured 
  by 
  Nicolet 
  as 
  furnished 
  with 
  a 
  crest 
  of 
  

   blunt, 
  tuberculiform 
  teeth 
  on 
  its 
  inner 
  border, 
  whereas 
  Milne-Edwards 
  

   distinctly 
  says 
  that 
  there 
  are 
  neither 
  teeth 
  nor 
  tubercles 
  upon 
  the 
  carpus 
  

   of 
  .4. 
  chilensis. 
  I 
  therefore 
  propose 
  to 
  call 
  Nicolet's 
  crayfish 
  Parastacus 
  

   nicoletii 
  (= 
  Astacus 
  chilensis 
  Nicolet 
  nee 
  Milne-Edwards). 
  

  

  Parastacus 
  hassleri 
  is 
  similar 
  to 
  P. 
  nicoletii. 
  That 
  both 
  of 
  them 
  are 
  

   fossorial 
  in 
  their 
  habits 
  is 
  evinced 
  by 
  the 
  marked 
  compression 
  of 
  the 
  

   cephalo-thorax, 
  small 
  size 
  of 
  the 
  first 
  abdominal 
  segment, 
  etc. 
  The 
  

   followirig 
  comparison 
  will 
  make 
  clear 
  the 
  chief 
  specific 
  differences 
  

   between 
  the 
  two 
  species: 
  In 
  P. 
  nicoletii 
  the 
  anteriov 
  part 
  of 
  the 
  sides 
  of 
  

   the 
  carapace 
  is 
  covered 
  with 
  fine 
  spinules; 
  in 
  P. 
  hassleri 
  these 
  spinules 
  

   are 
  replaced 
  by 
  a 
  small 
  group 
  of 
  blunt 
  tubercles. 
  In 
  P. 
  nicoletii 
  the 
  ros- 
  

   trum 
  does 
  not 
  overreach 
  the 
  proximal 
  end 
  of 
  the 
  second 
  segment 
  of 
  

   the 
  antennular 
  peduncle; 
  it 
  is 
  quadrate 
  in 
  form, 
  with 
  straight 
  and 
  jiar- 
  

   allel 
  lateral 
  margins, 
  its 
  upper 
  surface 
  deeply 
  concave. 
  In 
  P. 
  hassleri 
  

   the 
  rostrum 
  is 
  longer, 
  attaining 
  almost 
  to 
  the 
  distal 
  extremity 
  of 
  the 
  

   second 
  segment 
  of 
  the 
  antennular 
  peduncle; 
  its 
  upper 
  surface 
  is 
  but 
  

   lightly 
  hollowed 
  out, 
  while 
  its 
  lateral 
  borders 
  are 
  distinctly 
  convergent 
  

   from 
  the 
  base 
  forward. 
  The 
  carpus 
  of 
  P. 
  nicoletii 
  is 
  furnished 
  with 
  a 
  

   conspicuous 
  crest 
  of 
  rounded, 
  tuberculiform 
  teeth 
  along 
  its 
  inner 
  supe- 
  

   rior 
  border, 
  and 
  the 
  outline 
  of 
  the 
  opposite, 
  lower 
  or 
  external 
  border 
  

   is 
  extremely 
  convex 
  or 
  protuberant. 
  In 
  P. 
  hassleri 
  the 
  tubercular 
  

   crest 
  is 
  obsolete, 
  being 
  represented 
  merely 
  by 
  a 
  few 
  lightly 
  pronounced 
  

   denticles; 
  the 
  lower 
  or 
  external 
  border 
  is 
  but 
  slightly 
  convex, 
  whereby 
  

   the 
  carpus 
  comes 
  to 
  have 
  a 
  triangular 
  outline. 
  Finally, 
  the 
  hand 
  of 
  

   P. 
  hassleri 
  is 
  much 
  longer 
  than 
  that 
  of 
  P. 
  riicoletii, 
  its 
  upper 
  border 
  

   longer, 
  straighter, 
  and 
  less 
  strongly 
  tuberculate, 
  the 
  fingers 
  less 
  deeply 
  

   sulcated. 
  

  

  According 
  to 
  Nicolet, 
  crayfishes 
  are 
  found 
  in 
  the 
  rivers, 
  brooks, 
  and 
  

   even 
  in 
  the 
  forests, 
  of 
  southern 
  Chile, 
  where 
  they 
  live 
  in 
  holes 
  in 
  the 
  

   ground, 
  around 
  the 
  entrance 
  of 
  which 
  they 
  construct 
  earthworks 
  in 
  

   the 
  shape 
  of 
  a 
  cone 
  nearly 
  a 
  foot 
  in 
  height. 
  As 
  is 
  well 
  known. 
  Cam 
  

   bar 
  us 
  diogenes 
  Girard, 
  erects 
  similar 
  mud 
  towers 
  or 
  "chimneys" 
  in 
  the 
  

  

  'Gay's 
  Historia 
  Fisica 
  y 
  Politica 
  de 
  Chile, 
  Zoologia, 
  III, 
  p. 
  211; 
  Atlas, 
  II, 
  Crus- 
  

   tiiceos, 
  pi. 
  I, 
  fig, 
  4. 
  

  

  Proc. 
  N. 
  M. 
  vol. 
  XX 
  44 
  

  

  