﻿228 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  known; 
  longitudinally 
  grooved; 
  periodic 
  depressions 
  or 
  large 
  pits 
  

   in 
  the 
  grooves; 
  shown 
  as 
  blunt 
  spines 
  on 
  the 
  rock 
  mold. 
  

  

  Fig. 
  160 
  Ceratiocaris 
  ( 
  Phasganocaris 
  ? 
  ) 
  deweyi. 
  Telson 
  (reduced) 
  

  

  Found 
  in 
  the 
  Lockport 
  limestone 
  at 
  Niagara 
  ; 
  also 
  in 
  the 
  shale 
  at 
  

   Lockport 
  (Hall). 
  

  

  Order 
  eurypte^ridj^ 
  Burmeister 
  

  

  The 
  eurypterids 
  are 
  large 
  Crustacea, 
  with 
  an 
  elongate 
  body 
  com- 
  

   posed 
  of 
  cephalothorax, 
  a 
  ringed 
  abdomen, 
  and 
  a 
  tail 
  piece 
  or 
  telson. 
  

   The 
  body 
  is 
  covered 
  by 
  a 
  chitinous 
  epidermal 
  skeleton, 
  and 
  could 
  

   be 
  cast 
  off 
  as 
  in 
  the 
  modern 
  horseshoe 
  crab 
  (Limulus). 
  The 
  

   cephalothorax 
  is 
  usually 
  furnished 
  dorsally 
  with 
  two 
  large, 
  facetted 
  

   lateral 
  eyes, 
  and 
  a 
  pair 
  of 
  median 
  ocelli; 
  and 
  ventrally 
  with 
  six 
  pairs 
  

   of 
  legs. 
  The 
  anterior 
  joints 
  or 
  rings 
  of 
  the 
  abdomen 
  bear 
  on 
  their 
  

   under 
  side 
  five 
  pairs 
  of 
  broad, 
  leaf-like 
  appendages, 
  which 
  are 
  com- 
  

   parable 
  to 
  the 
  gills 
  and 
  operculum 
  of 
  the 
  horseshoe 
  crab. 
  The 
  

   posterior 
  six 
  segments 
  are 
  without 
  appendages. 
  The 
  legs 
  are 
  com- 
  

   parable 
  to 
  those 
  of 
  Limulus 
  and, 
  like 
  them, 
  their 
  inner 
  margins 
  are 
  

   furnished 
  with 
  stout 
  spines 
  which 
  serve 
  as 
  teeth. 
  The 
  last 
  pair 
  of 
  

   legs 
  is 
  generally 
  large, 
  and 
  usually 
  somewhat 
  flattened, 
  and 
  ends 
  in 
  

   an 
  oval 
  plate. 
  This 
  " 
  paddle 
  " 
  may 
  have 
  been 
  used 
  for 
  swimming 
  

   purposes 
  or 
  for 
  purposes 
  of 
  anchoring. 
  On 
  the 
  under 
  or 
  ventral 
  

   surfaces 
  of 
  the 
  first 
  two 
  abdominal 
  segments 
  is 
  the 
  genital 
  oper- 
  

   culum, 
  a 
  pair 
  of 
  plates 
  meeting 
  medially, 
  with 
  a 
  median 
  lobe 
  at- 
  

   tached 
  which 
  differs 
  in 
  the 
  two 
  sexes. 
  

  

  Genus 
  eurypterus 
  DeKay 
  

  

  [Ety. 
  : 
  edpu<^, 
  broad; 
  Tzrapov, 
  wing] 
  

  

  (1825. 
  Lye. 
  nat. 
  hist. 
  N. 
  Y. 
  An. 
  1:375) 
  

  

  Body 
  elongate 
  and 
  narrow, 
  often 
  of 
  great 
  size. 
  Cephalothorax 
  

   one 
  fifth 
  or 
  one 
  sixth 
  of 
  the 
  whole 
  length, 
  depressed 
  convex, 
  of 
  a 
  

   subquadrate 
  outline 
  with 
  the 
  anterior 
  angles 
  rounded, 
  and 
  the 
  pos- 
  

   terior 
  margin 
  slightly 
  concave; 
  entire 
  margin 
  bordered 
  by 
  a 
  narrow 
  

   marginal 
  furrow. 
  Eyes 
  reniform, 
  situated 
  somewhat 
  in 
  front 
  of 
  the 
  

   middle; 
  ocelli 
  close 
  to 
  the 
  axial 
  line. 
  Mouth 
  a 
  ventral 
  cleft. 
  Legs 
  

  

  