﻿NO. 
  1136. 
  OBSERVATIONS 
  ON 
  THE 
  ASTACIDJi—FAXOX. 
  671 
  

  

  The 
  telson 
  of 
  the 
  specimen 
  figured 
  by 
  Heller 
  is 
  more 
  spiny 
  than 
  usual. 
  

  

  This 
  species 
  Avas 
  first 
  described 
  by 
  Shaw 
  as 
  Cancer 
  serratua, 
  a 
  name 
  

   already 
  used 
  by 
  Forskal 
  for 
  a 
  different 
  animal, 
  Set/Ua 
  serrata. 
  Follow- 
  

   ing 
  the 
  American 
  Ornithologists' 
  Union 
  Committee's 
  code 
  of 
  nomencla- 
  

   ture,' 
  the 
  name 
  si>rr((tfi.s 
  must 
  be 
  discarded 
  in 
  favor 
  of 
  sjnn 
  if 
  er 
  of 
  Heller. 
  

  

  The 
  number 
  and 
  arrangement 
  of 
  the 
  gills 
  are 
  the 
  same 
  as 
  in 
  A. 
  

   franklinii, 
  as 
  shown 
  in 
  the 
  formula 
  on 
  page 
  G69. 
  But 
  the 
  inner 
  wajl 
  

   of 
  the 
  stem 
  of 
  all 
  the 
  podobranchia^, 
  except 
  the 
  hindmost, 
  develops 
  

   a 
  broad 
  limb 
  or 
  ala, 
  as 
  in 
  the 
  genus 
  CJieraps; 
  this 
  ala, 
  however, 
  bears 
  

   long 
  hair-like 
  seta? 
  in 
  place 
  of 
  the 
  hooked 
  branchial 
  filaments 
  seen 
  

   in 
  Cheraps. 
  In 
  A. 
  franklinii 
  this 
  ala 
  is 
  very 
  rudimentary, 
  in 
  which 
  

   regard 
  that 
  species 
  shows 
  agaiji 
  its 
  affinity 
  to 
  Astaco'ides 
  madagasca- 
  

   rieusis. 
  The 
  epipod 
  of 
  tlie 
  first 
  maxilliped 
  bears 
  a 
  large 
  number 
  of 
  

   hookless 
  branchial 
  filaments. 
  

  

  Genus 
  CHERAPS 
  Erichson. 
  

   Cheraps 
  EiuCHSOX, 
  Arch. 
  f. 
  Xatiirgesch., 
  12t('r 
  .lahi's., 
  I, 
  p. 
  101, 
  ISlti. 
  

   Type, 
  Astacus 
  [Ch(ra2)>i) 
  j'l'cisnii 
  ILrichson. 
  

  

  Eostrum 
  rather 
  narrow, 
  triangular, 
  plane 
  or 
  even 
  a 
  little 
  convex 
  

   above, 
  obscurely 
  marginate, 
  entire 
  or 
  obscurely 
  toothed 
  near 
  the 
  ti}). 
  

   Antenna! 
  scale 
  broadly 
  oval, 
  or 
  often 
  broadly 
  truncate 
  at 
  the 
  distal 
  

   end. 
  Anterior 
  process 
  of 
  epistome 
  broadly 
  triangular. 
  Superior 
  border 
  

   of 
  hand 
  with 
  a 
  denticulated 
  carina. 
  Carapace 
  and 
  abdomen 
  smooth, 
  

   nearly 
  free 
  from 
  spines 
  and 
  tubercles; 
  areola 
  narrow. 
  Distal 
  moiety 
  

   of 
  telson 
  and 
  of 
  both 
  branches 
  of 
  the 
  posterior 
  abdominal 
  appendages 
  

   membranaceous; 
  median 
  carina 
  of 
  inner 
  branch 
  of 
  the 
  latter 
  terminat- 
  

   ing 
  in 
  a 
  small 
  spine 
  near 
  the 
  middle 
  of 
  the 
  segment; 
  transverse 
  suture 
  

   of 
  the 
  outer 
  branch 
  halfway 
  between 
  the 
  proximal 
  and 
  distal 
  ends. 
  

   Form 
  cambaroid. 
  Gills 
  forty-two 
  (one 
  i)air 
  very 
  small 
  — 
  almost 
  rudi- 
  

   mentary), 
  disposed 
  as 
  shown 
  in 
  the 
  following 
  table 
  :- 
  

  

  Akthrobranchi^. 
  

  

  Somite. 
  Podobranchi^. 
  . 
  Pleubobranchlk. 
  

  

  Anterior. 
  Posterior. 
  

  

  VII. 
  . 
  . 
  . 
  O(epr) 
  . 
  . 
  . 
  . 
  . 
  . 
  . 
  . 
  . 
  . 
  = 
  (ep 
  »•) 
  

  

  VIII. 
  ...1....1....0....0 
  =2 
  

  

  IX. 
  ... 
  1 
  .... 
  1 
  .... 
  1 
  .... 
  =3 
  

  

  X. 
  ... 
  1 
  .... 
  1 
  .... 
  1 
  .... 
  = 
  .3 
  

  

  XI. 
  ... 
  1 
  .... 
  1 
  .... 
  1 
  .... 
  1 
  =4 
  

  

  XII. 
  ...1....1....1....1 
  =4 
  

  

  XIII. 
  ...l....l....al....l 
  =4 
  

  

  XIV. 
  ...0....0....0....1 
  =1 
  

  

  6-fep»- 
  +6 
  + 
  5 
  + 
  4 
  = 
  21-fep/- 
  

  

  a 
  Very 
  minute, 
  almost 
  rudimentary. 
  

  

  Hahitat. 
  — 
  Australia. 
  

  

  > 
  Canon 
  XXXIII. 
  

  

  ^ 
  The 
  arrangement 
  and 
  structure 
  of 
  the 
  branchial 
  apparatus 
  in 
  Cheraps 
  ^ 
  as, 
  lirst 
  

   described 
  by 
  Huxley, 
  from 
  an 
  undetermined 
  specimen 
  in 
  the 
  British 
  Museum 
  from 
  

   the 
  Yarra-Yarra 
  River, 
  Australia. 
  From 
  the 
  locality, 
  this 
  specimen 
  was 
  pre8umal)ly 
  

   Chi 
  raps 
  hicari)iatus. 
  I 
  have 
  examined 
  the 
  branchial 
  organs 
  in 
  si)ccimens 
  of 
  C. 
  hicar- 
  

   iuafus 
  in 
  the 
  Museum 
  of 
  Comparative 
  Zoology 
  and 
  find 
  that 
  they 
  agree 
  in 
  every 
  

   respect 
  with 
  Huxley's 
  description 
  (Proc. 
  Zool. 
  Soc. 
  London, 
  1878, 
  pp. 
  768. 
  7(i9, 
  tig. 
  

   6). 
  Erichson 
  was 
  manifestly 
  wrong 
  in 
  saying 
  that 
  Cheraps, 
  like 
  Cambarus, 
  lacked 
  

   gills 
  on 
  the 
  last 
  thoracic 
  somite. 
  

  

  