﻿THE 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [FOURTH 
  SERIES.] 
  

  

  Art. 
  XXIII. 
  — 
  The 
  Skull, 
  Pelvis, 
  and 
  Probable 
  Relationships 
  

   of 
  the 
  Huge 
  Turtles 
  of 
  the 
  Genus 
  Archelon 
  from 
  the 
  Fort 
  

   Jpierre 
  Cretaceous 
  of 
  South 
  Dakota 
  / 
  by 
  G-. 
  R. 
  Wieland. 
  

   With 
  Plate 
  II. 
  

  

  The 
  marine 
  turtles 
  of 
  the 
  Fort 
  Pierre 
  Cretaceous 
  of 
  South 
  

   Dakota 
  uot 
  only 
  represent 
  the 
  most 
  gigantic 
  species 
  known, 
  

   but 
  also 
  are 
  of 
  much 
  importance 
  as 
  including 
  undoubted 
  

   descendants 
  of 
  Protostega 
  from 
  the 
  underlying 
  Niobrara 
  Cre- 
  

   taceous, 
  in 
  common 
  with 
  which 
  they 
  may 
  be 
  regarded 
  as 
  

   ancient 
  relatives 
  of 
  Dermochelys. 
  

  

  The 
  first 
  of 
  these 
  turtles 
  was 
  discovered 
  and 
  collected 
  by 
  the 
  

   writer 
  in 
  1895. 
  The 
  nearly 
  complete 
  carapace, 
  pectoral 
  girdle 
  

   and 
  limb 
  bones 
  of 
  this 
  specimen 
  were 
  described 
  in 
  this 
  Journal 
  

   (13)* 
  the 
  year 
  following 
  as 
  those 
  of 
  the 
  new 
  genus 
  and 
  species 
  

   Archelon 
  ischyros. 
  Additional 
  material 
  collected 
  in 
  1897 
  and 
  

   1898, 
  and 
  in 
  part 
  here 
  described, 
  proves 
  this 
  determination 
  to 
  

   have 
  been 
  correct, 
  although 
  in 
  describing 
  the 
  fine 
  plastron 
  of 
  

   the 
  first 
  specimen 
  secured 
  the 
  generic 
  name 
  Protostega 
  was 
  

   needlessly 
  substituted 
  (15). 
  This 
  was 
  done 
  in 
  deference 
  to 
  

   high 
  authority, 
  but 
  careful 
  comparison 
  made 
  possible 
  by 
  new 
  

   material 
  of 
  both 
  Protostega 
  and 
  Archelon 
  places 
  beyond 
  

   further 
  question 
  the 
  validity 
  of 
  the 
  latter 
  genus. 
  

  

  The 
  Skull 
  of 
  Archelon 
  Ischyros 
  Wieland. 
  

   The 
  skull, 
  the 
  description 
  of 
  which 
  is 
  here 
  given, 
  was 
  secured 
  

   by 
  the 
  writer 
  in 
  the 
  summer 
  of 
  1897, 
  and- 
  belongs 
  to 
  the 
  

   second 
  specimen 
  discovered, 
  this 
  being 
  nearly 
  complete. 
  Not- 
  

   withstanding 
  its 
  gigantic 
  size, 
  it 
  represents 
  a 
  turtle 
  only 
  three- 
  

   fifths 
  as 
  large 
  as 
  specimen 
  I. 
  A 
  fragmentary 
  specimen 
  (III) 
  

  

  *See 
  references 
  on 
  p. 
  250. 
  

  

  Am. 
  Jour. 
  Scr. 
  — 
  Fourtii 
  Series, 
  Vol. 
  IX, 
  No. 
  52. 
  — 
  April, 
  1900. 
  

   17 
  

  

  