﻿232 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  A1VOMODOXTIA. 
  

  

  y 
  

  

  Dicynodon 
  Owen. 
  

   Dicynodon 
  rosmarus 
  Cope 
  sp. 
  nov. 
  

  

  A 
  species 
  of 
  this 
  genus 
  occurs 
  in 
  the 
  Triassic 
  beds 
  of 
  Pennsylvania, 
  thus 
  completing 
  

   the 
  similarity 
  between 
  them 
  and 
  the 
  Trias 
  of 
  S. 
  Africa 
  and 
  India 
  in 
  the 
  combination 
  with 
  

   Labyrinthodonts 
  (Eupelor), 
  Thecodonts 
  (Belodon), 
  and 
  Dinosauria 
  (Clepsysaurus). 
  The 
  

   species 
  is 
  represented 
  by 
  two 
  shed 
  canine 
  teeth, 
  one 
  specimen 
  represented 
  by 
  the 
  root 
  of 
  the 
  

   fang 
  only. 
  They 
  indicate 
  one 
  of 
  the 
  larger 
  species, 
  the 
  root 
  being 
  about 
  nine 
  lines 
  in 
  diame- 
  

   ter 
  at 
  the 
  basis, 
  the 
  crown 
  rather 
  strongly 
  curved. 
  Section 
  a 
  wide 
  oval, 
  more 
  circular 
  near 
  

   the 
  apex. 
  Other 
  remains, 
  more 
  characteristic, 
  will 
  shortly 
  be 
  described. 
  

  

  From 
  the 
  " 
  red 
  bed 
  " 
  of 
  Wheatley's 
  section 
  at 
  the 
  tunnel 
  at 
  Phcenixville, 
  Chester 
  Co., 
  

   Pa., 
  Museum 
  of 
  Chas. 
  M. 
  Wheatley, 
  A.M., 
  to 
  whom 
  I 
  am 
  indebted 
  for 
  the 
  loan 
  of 
  the 
  

   specimens. 
  

  

  TESTUDIMTA. 
  

  

  Adocus, 
  Cope. 
  

  

  Proceed. 
  Acad. 
  Natl. 
  Sciences, 
  Phila., 
  1868, 
  335. 
  

  

  Character. 
  Anterior 
  and 
  posterior 
  lobes 
  of 
  the 
  plastron 
  abbreviated, 
  narrowed, 
  and 
  not 
  emarginate. 
  Eight 
  paired 
  

   sternal 
  bones 
  ; 
  twelve 
  sternal 
  scuta, 
  the 
  numerals 
  extending 
  anteriorly, 
  the 
  pectorals 
  and 
  gulars 
  both 
  small. 
  A 
  series 
  

   of 
  plates, 
  " 
  intermarginals 
  " 
  within 
  the 
  marginals, 
  on 
  the 
  sternal 
  bridge. 
  Eib 
  heads, 
  i. 
  e., 
  the 
  capitula, 
  wanting 
  in 
  

   the 
  species 
  whose 
  costals 
  have 
  been 
  examined. 
  

  

  This 
  genus 
  was 
  originally 
  described 
  with 
  Emys 
  Meatus 
  Leidy 
  from 
  the 
  Cretaceous 
  Green 
  Sand 
  of 
  New 
  Jersey, 
  as 
  the 
  

   type, 
  and 
  its 
  primary 
  character 
  was 
  regarded 
  as 
  the 
  absence 
  of 
  the 
  costal 
  capitula. 
  In 
  the 
  synopsis 
  of 
  extinct 
  rep- 
  

   tilia 
  of 
  New 
  Jersey, 
  published 
  in 
  Prof. 
  Cook's 
  Geological 
  Survey 
  of 
  that 
  State, 
  five 
  species 
  were 
  enumerated, 
  as 
  

   follows 
  : 
  A. 
  petrosus 
  Cope, 
  A. 
  firrnus 
  Leidy, 
  A. 
  beatus 
  Leidy. 
  A. 
  pravus 
  Leidy, 
  and 
  A. 
  agilis 
  Cope. 
  The 
  two 
  species 
  

   first 
  enumerated 
  having 
  subsequently 
  been 
  found 
  to 
  possess 
  well 
  developed 
  costal 
  capitula 
  ; 
  I 
  referred 
  them 
  to 
  Emys, 
  

   in 
  the 
  present 
  work, 
  p. 
  126. 
  My 
  specimens 
  of 
  A. 
  agilis 
  being 
  at 
  the 
  time 
  very 
  imperfect, 
  it 
  was 
  not 
  described. 
  

  

  At 
  present, 
  I 
  propose 
  to 
  point 
  out 
  its 
  characters, 
  as 
  well 
  as 
  those 
  of 
  the 
  other 
  species 
  of 
  the 
  genus. 
  Two 
  species 
  

   are 
  added, 
  the 
  whole 
  number 
  being 
  then 
  five. 
  One 
  of 
  these 
  is 
  from 
  the 
  Cretaceous 
  deposits 
  of 
  Wyoming, 
  the 
  others 
  

   from 
  New 
  Jersey. 
  

  

  The 
  plastron 
  in 
  this 
  genus 
  presents 
  marked 
  peculiarity. 
  The 
  great 
  reduction 
  of 
  the 
  anterior 
  and 
  posterior 
  lobes 
  

   gives 
  it 
  a 
  form 
  approximating 
  that 
  of 
  Staurotypus. 
  The 
  anal 
  scuta 
  are 
  of 
  large 
  size, 
  and 
  the 
  femoral 
  abdominal 
  

   scutal 
  suture 
  (in 
  A. 
  agilis) 
  extends 
  across 
  just 
  in 
  advance 
  of 
  the 
  inguinal 
  notch. 
  The 
  abdominal 
  is 
  the 
  widest 
  pair 
  

   of 
  scuta, 
  in 
  consequence 
  of 
  the 
  relatively 
  great 
  longitudinal 
  extent 
  of 
  the 
  bridge; 
  their 
  anterior 
  outline 
  falls 
  a 
  little 
  be- 
  

   hind 
  the 
  axillary 
  notch. 
  The 
  humeral 
  scuta 
  have 
  a 
  remarkable 
  anterior 
  extent, 
  so 
  much 
  so 
  as 
  to 
  lead 
  to 
  the 
  suspicion 
  

   that 
  they 
  were 
  confluent 
  with 
  the 
  pectorals, 
  or 
  perhaps 
  wanting. 
  In 
  the 
  case 
  of 
  A. 
  pectoralis, 
  having 
  only 
  the 
  hyos- 
  

   ternal 
  bones, 
  I 
  was 
  induced 
  to 
  think 
  that 
  they 
  were 
  really 
  the 
  pectorals, 
  and 
  that 
  the 
  abdominals 
  were 
  the 
  true 
  

   numerals, 
  as 
  is 
  seen 
  in 
  the 
  genus 
  Pleurosternum; 
  the 
  posterior 
  position 
  of 
  the 
  humerals 
  in 
  the 
  latter 
  being 
  owing 
  to 
  

   the 
  existence 
  of 
  an 
  additional 
  pair 
  of 
  sternal 
  bones. 
  An 
  examination 
  of 
  the 
  structure 
  in 
  A. 
  agilis, 
  and 
  A. 
  wyomingen- 
  

   sis 
  dispels 
  this 
  view, 
  and 
  shows 
  that 
  the 
  true 
  pectorals 
  are 
  much 
  shortened, 
  and 
  have 
  an 
  anterior 
  position, 
  and 
  that 
  

   the 
  gulars 
  are 
  also 
  small 
  and 
  narrowed, 
  the 
  genus 
  approaching 
  Chelydra 
  in 
  these 
  respects. 
  

  

  The 
  lateral 
  series 
  of 
  abdominal 
  marginals 
  is 
  seen 
  in 
  the 
  existing 
  genera 
  Macrochelys 
  and 
  Dermatcmys. 
  The 
  

   affinity 
  of 
  Adocus 
  is 
  to 
  the 
  latter, 
  but 
  the 
  entire 
  acuminate 
  free 
  lobes 
  of 
  the 
  plastron 
  distinguish 
  it 
  well. 
  The 
  lateral 
  

   marginal 
  scuta 
  in 
  A. 
  agilis, 
  A. 
  wyomingensis 
  and 
  A. 
  pectoralis 
  are 
  very 
  distinct 
  in 
  our 
  specimens, 
  while 
  I 
  have 
  seen 
  it 
  

   in 
  only 
  one 
  of 
  the 
  two 
  or 
  three 
  in 
  which 
  the 
  bridge 
  is 
  preserved 
  in 
  A. 
  beatus. 
  In 
  A. 
  pravus, 
  I 
  have 
  not 
  seen 
  it, 
  but 
  

  

  