﻿OF 
  THE 
  BALTIC 
  PROVINCES 
  OF 
  RUSSIA. 
  529 
  

  

  been 
  collecting 
  at 
  Rotzikiill 
  upon 
  several 
  occasions, 
  and 
  I 
  have 
  now 
  

   brought 
  together 
  such 
  a 
  large 
  mass 
  of 
  materials, 
  that 
  nearly 
  all 
  the 
  

   small 
  details 
  of 
  the 
  structure 
  can 
  be 
  explained 
  thereby. 
  Nieszkow- 
  

   ski, 
  in 
  his 
  paper 
  on 
  Eurypterus 
  (Dorpat, 
  1858), 
  assumed 
  six 
  free 
  

   thoracic 
  plates 
  ; 
  I 
  cannot 
  now 
  detect 
  more 
  than 
  five, 
  but 
  this 
  number 
  

   is 
  indubitable 
  ; 
  and 
  I 
  cannot 
  agree 
  with 
  Dr. 
  H. 
  Woodward, 
  who, 
  ac- 
  

   cording 
  to 
  Prof. 
  J. 
  Hall's 
  detailed 
  but 
  insufficient 
  description, 
  does 
  

   not 
  assume 
  more 
  than 
  one 
  of 
  such 
  thoracic 
  plates. 
  Certainly 
  there 
  

   has 
  been 
  a 
  misconception 
  on 
  the 
  part 
  of 
  Nieszkowski 
  as 
  to 
  the 
  cen- 
  

   tral 
  appendage 
  ; 
  but 
  the 
  positive 
  existence 
  of 
  five 
  free 
  plates 
  (corre- 
  

   sponding 
  to 
  six 
  in 
  Limulus) 
  I 
  shall 
  be 
  able 
  to 
  prove 
  by 
  numerous 
  

   figures, 
  taken 
  from 
  original 
  specimens, 
  and 
  by 
  a 
  detailed 
  description. 
  

   A 
  second 
  discovery 
  is 
  a 
  large 
  Pterygotus, 
  an 
  intimate 
  ally 
  of 
  P. 
  

   gigas, 
  Salt., 
  but 
  probably 
  a 
  new 
  species. 
  JSTo 
  wholly 
  preserved 
  speci- 
  

   mens 
  are 
  found 
  ; 
  but 
  I 
  possess 
  all 
  necessary 
  details, 
  with 
  the 
  exception 
  

   of 
  the 
  telson. 
  Of 
  peculiar 
  interest 
  also 
  are 
  three 
  species 
  of 
  the 
  genus 
  

   Bunodes, 
  Eichw., 
  namely 
  B. 
  lunula, 
  Eichw., 
  B. 
  rugosus, 
  Nieszk., 
  

   and 
  B. 
  Schrenckii, 
  Nieszk., 
  sp., 
  (Exapinurus 
  Schrenckii, 
  Meszk.), 
  

   and 
  Pseudoniscus 
  aculeatus, 
  Nieszk. 
  Both 
  genera 
  are 
  perhaps 
  

   most 
  nearly 
  allied 
  to 
  the 
  British 
  genus 
  Hemiaspis, 
  Salt., 
  as 
  I 
  was 
  

   kindly 
  convinced 
  by 
  Dr. 
  H. 
  Woodward, 
  on 
  my 
  visit 
  to 
  the 
  British 
  

   Museum 
  in 
  1875. 
  Dr. 
  Woodward 
  enumerates 
  Hemiaspis 
  among 
  

   the 
  Eurypterida 
  ; 
  but 
  I 
  believe 
  that 
  the 
  three 
  genera 
  Hemiaspis, 
  Bu- 
  

   nodes, 
  and 
  Pseudoniscus 
  should 
  form 
  a 
  distinct 
  family 
  intermediate 
  

   between 
  Eurypterida 
  and 
  Trilobites. 
  The 
  want 
  of 
  strongly 
  developed 
  

   swimming-feet 
  and 
  other 
  appendages 
  on 
  the 
  lower 
  side 
  of 
  the 
  head, 
  

   the 
  distinct 
  trilobation 
  of 
  the 
  thorax, 
  and 
  the 
  chemical 
  constitution 
  

   of 
  the 
  carapace 
  (which 
  is 
  always 
  destroyed 
  in 
  dolomites, 
  like 
  that 
  of 
  

   Trilobites, 
  while 
  the 
  chitinous 
  covering 
  of 
  Eurypterida 
  even 
  in 
  dolo- 
  

   mites 
  is 
  beautifully 
  preserved) 
  show 
  the 
  difference 
  of 
  the 
  Hemiaspida 
  

   and 
  Eurypterida, 
  and 
  the 
  near 
  relation 
  of 
  the 
  former 
  to 
  Trilobites, 
  

   with 
  which 
  group 
  the 
  genus 
  Bunodes 
  was 
  formerly 
  classed 
  by 
  Eich- 
  

   wald, 
  in 
  his 
  ' 
  Lethaea 
  Rossica.' 
  Besides 
  the 
  above-named 
  crustaceans, 
  

   I 
  have 
  yet 
  to 
  mention 
  a 
  large 
  form 
  of 
  the 
  Ceratiocaris-growp, 
  the 
  new 
  

   genus 
  Cardiocaris, 
  with 
  a 
  large 
  cordiform 
  dorsal 
  shield, 
  somewhat 
  

   similar 
  to 
  the 
  Carboniferous 
  Dithyrocaris, 
  Scouler. 
  Of 
  other 
  classes 
  

   in 
  the 
  Eurypterus-DolomitQ 
  there 
  occur 
  an 
  Ortlioceras, 
  0. 
  tenue, 
  

   Eichw., 
  with 
  the 
  shell 
  destroyed, 
  and 
  two 
  interesting 
  Cephalaspidian 
  

   fishes, 
  Thyestes 
  verrucosus, 
  Eichw., 
  and 
  Tremataspis 
  Schrenckii, 
  Pand., 
  

   mihi, 
  formerly 
  figured 
  and 
  described 
  by 
  me 
  in 
  1866, 
  in 
  the 
  'Yer- 
  

   haudlungen 
  ' 
  of 
  the 
  St. 
  Petersburg 
  Miner 
  alogical 
  Society. 
  The 
  

   Eury2)terus-stra,ta, 
  are 
  overlain 
  by 
  thin 
  marly 
  flags 
  filled 
  with 
  

   the 
  typical 
  English 
  Platyschisma 
  helicoides, 
  Sow., 
  together 
  with 
  

   numerous 
  specimens 
  of 
  Leperditia 
  phaseolv.s, 
  His. 
  (Angelini, 
  mihi), 
  

   and 
  small 
  fish-scales 
  of 
  the 
  genus 
  Coelolepis, 
  Pand., 
  and 
  other 
  

   minute 
  fish-remains. 
  Then 
  follow 
  the 
  before-mentioned 
  yellow 
  

   limestones 
  with 
  Murchisonia 
  cingidata, 
  M. 
  didyma, 
  and 
  Chonetes 
  

   striatella. 
  In 
  the 
  island 
  of 
  Gothland 
  the 
  same 
  species 
  of 
  Eurypterus 
  

   is 
  also 
  met 
  at 
  the 
  base 
  of 
  the 
  uppermost 
  Silurian 
  stage, 
  near 
  Oes- 
  

   tergari, 
  and 
  the 
  same 
  is 
  also 
  the 
  case 
  in 
  Podolia 
  on 
  the 
  Dniester. 
  

  

  