﻿686 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  

  

  of 
  the 
  thirteenth 
  somite 
  is 
  reduced 
  to 
  a 
  small, 
  simple 
  filament. 
  The 
  

   podobranchia^ 
  are 
  alate 
  and 
  the 
  alu' 
  are 
  provided 
  with 
  hooked 
  tubercles 
  

   similar 
  to 
  those 
  of 
  the 
  Astacinw. 
  The 
  coxopoditic 
  setic 
  are 
  long 
  and 
  

   hooked 
  at 
  the 
  end. 
  

  

  Habitat.— 
  (Johmii, 
  Mexico. 
  J. 
  Xautus. 
  (No. 
  4133, 
  Coll. 
  U.S.KM.) 
  

   One 
  specimen. 
  

  

  The 
  locality 
  is 
  notable 
  as 
  being 
  the 
  only 
  one 
  north 
  of 
  the 
  equator 
  

   where 
  Parastacine 
  crayfishes 
  occur. 
  Furthermore, 
  the 
  close 
  affinity 
  

   between 
  this 
  species 
  and 
  a 
  native 
  of 
  Uruguay 
  [Parastacus 
  saffordi) 
  is 
  

   surj)rising. 
  But 
  beyond 
  this 
  there 
  appears 
  to 
  be 
  no 
  reason 
  to 
  discredit 
  

   the 
  legend 
  which 
  accompanies 
  the 
  type 
  specimen 
  of 
  P. 
  varicosus 
  in 
  the 
  

   United 
  States 
  National 
  Museum. 
  

  

  PARASTACUS 
  DEFOSSUS, 
  new 
  species. 
  

  

  (Plate 
  LXVII, 
  tigs. 
  3,4.) 
  

  

  Cephalo-thorax 
  laterally 
  compressed, 
  the 
  sideshigh 
  and 
  nearly 
  vertical. 
  

   Anterior 
  segment 
  of 
  abdomen 
  small. 
  Rostrum 
  small, 
  triangular, 
  defiexed, 
  

   plane 
  above, 
  lateral 
  borders 
  slightly 
  marginate, 
  strongly 
  converging 
  from 
  

   the 
  base 
  to 
  the 
  blunt 
  tip 
  which 
  hardly 
  reaches 
  to 
  the 
  proximal 
  end 
  of 
  the 
  

   third 
  antennular 
  segment. 
  The 
  margins 
  of 
  the 
  rostrum 
  are 
  prolonged 
  

   backward 
  for 
  a 
  short 
  distance 
  on 
  the 
  gastric 
  area, 
  where 
  they 
  teiul 
  to 
  

   fuse 
  with 
  the 
  anterior 
  end 
  of 
  the 
  postorbital 
  ridges. 
  The 
  latter 
  are 
  

   but 
  slightly 
  marked, 
  unarmed, 
  strongly 
  divergent 
  in 
  their 
  backward 
  

   course. 
  The 
  suborbital 
  angle 
  is 
  prominent, 
  but 
  perfectly 
  rounded 
  ofi\ 
  

   The 
  dorsal 
  surface 
  of 
  the 
  carapace 
  is 
  smooth, 
  polished, 
  and 
  sparsely 
  

   j)unctate, 
  the 
  lateral 
  walls 
  lightly 
  granulate. 
  The 
  areola 
  is 
  very 
  long 
  

   and 
  narrow, 
  the 
  gastric 
  area 
  proportionally 
  short. 
  Abdominal 
  pleune 
  

   rounded, 
  telson 
  long, 
  posteriorly 
  oval 
  in 
  outline. 
  Anterior 
  process 
  of 
  

   epistome 
  rather 
  long, 
  but 
  slightly 
  separated 
  from 
  the 
  body 
  of 
  the 
  

   epistome 
  by 
  transverse 
  suture; 
  anteriorly 
  truncate. 
  Antennn? 
  about 
  

   equal 
  in 
  length 
  to 
  the 
  cephalo-thorax 
  j 
  scale 
  small, 
  broad, 
  broadest 
  

   near 
  the 
  distal 
  end, 
  external 
  border 
  terminating 
  in 
  a 
  long, 
  stout 
  spine 
  

   directed 
  a 
  little 
  outward 
  ; 
  a 
  blunt 
  spine 
  or 
  tubercle 
  on 
  the 
  lower 
  side 
  of 
  

   the 
  first 
  antennal 
  segment, 
  just 
  in 
  front 
  of 
  the 
  orifice 
  of 
  the 
  green 
  

   gland; 
  no 
  external 
  spine 
  at 
  base 
  of 
  the 
  scale. 
  Third 
  maxillij)eds 
  hairy 
  

   within. 
  Chelipeds 
  symmetrical 
  ; 
  merus 
  trigonal, 
  outer 
  face 
  smooth, 
  infe- 
  

   rior 
  edges 
  serrate, 
  superior 
  edge 
  armed 
  with 
  one 
  blunt 
  tooth 
  near 
  the 
  

   distal 
  end; 
  carpus 
  broadly 
  triangular, 
  internal 
  border 
  armed 
  with 
  a 
  

   single 
  series 
  of 
  blunt 
  teeth 
  which 
  increase 
  in 
  size 
  toward 
  the 
  distal 
  end 
  

   of 
  the 
  segment; 
  hand 
  short 
  and 
  broad, 
  the 
  palm 
  as 
  broad 
  as 
  long, 
  outer 
  

   face 
  convex, 
  smooth, 
  with 
  scattering 
  coarse 
  puncta, 
  superior 
  (or 
  internal) 
  

   margin 
  ornamented 
  with 
  a 
  low 
  crest 
  of 
  squamous, 
  setiferous 
  tubercles, 
  

   inferior 
  border 
  similarly 
  adorned 
  with 
  single 
  row 
  of 
  tubercles 
  running 
  

   from 
  the 
  proximal 
  end 
  of 
  the 
  haiul 
  as 
  far 
  as 
  to 
  the 
  base 
  of 
  the 
  immo- 
  

   bile 
  finger, 
  where 
  they 
  are 
  replaced 
  by 
  shallow 
  pits; 
  dactylus 
  equal 
  in 
  

   length 
  to 
  the 
  breadth 
  of 
  the 
  hand, 
  upper 
  margin 
  rounded, 
  with 
  a 
  single 
  

  

  