﻿AND 
  AYES 
  OF 
  NORTH 
  AMERICA. 
  151 
  

  

  TRIONYX, 
  Geoffr. 
  

   Costal 
  bone 
  transversely 
  figured 
  by 
  narrow 
  elevated 
  ridges. 
  t. 
  lima. 
  

  

  Costal 
  bone 
  with 
  thick, 
  low 
  transverse 
  ridges, 
  which 
  are 
  connected 
  by 
  cross-ribs, 
  

   which 
  leave 
  series 
  of 
  pits. 
  

  

  T. 
  PRISCUS. 
  

  

  Costal 
  bones 
  with 
  transverse 
  irregular 
  grooves 
  proximally, 
  which 
  remain 
  along 
  the 
  

   suture 
  only 
  distally, 
  leaving 
  a 
  triangular 
  area 
  of 
  a 
  shallow 
  honey-comb 
  pattern 
  medially. 
  

  

  Large, 
  massive; 
  the 
  grooves 
  of 
  the 
  shell 
  widens 
  the 
  intervening 
  ridges. 
  

  

  T. 
  PENNATUS. 
  

  

  Smaller, 
  light; 
  the 
  grooves 
  much 
  wider 
  than 
  the 
  fine 
  separating 
  ridges. 
  

  

  T. 
  BUIEI. 
  

  

  Costal 
  bones, 
  with 
  a 
  shallow, 
  coarse 
  honey-comb 
  pattern, 
  tending 
  to 
  confluence 
  dis- 
  

   tally. 
  

  

  The 
  vertebral 
  segments 
  shorter 
  and 
  wider 
  ; 
  shell 
  heavy, 
  much 
  arched. 
  

  

  T. 
  HALOPHILUS. 
  

  

  The 
  vertebral 
  segments 
  of 
  the 
  carapace 
  long 
  and 
  narrow 
  ; 
  shell 
  thinner, 
  fiat. 
  

  

  T. 
  GUTTATUS. 
  

  

  TRIONYX 
  HALOPHILUS, 
  Cope. 
  

  

  Proc. 
  A. 
  N. 
  Sci., 
  Phila., 
  18G9, 
  p. 
  12. 
  

  

  Established 
  upon 
  numerous 
  portions 
  of 
  vertebral 
  sternal 
  and 
  costal 
  plates, 
  from 
  near 
  Summit 
  Bridge, 
  Newcastle 
  

   Co., 
  Delaware, 
  and 
  from 
  Camden 
  Co., 
  New 
  Jersey- 
  both 
  from 
  the 
  lower 
  bed 
  of 
  marl, 
  according 
  to 
  Cook's 
  explana- 
  

   tion 
  of 
  the 
  Cretaceous 
  period. 
  

  

  This 
  species 
  differs 
  from 
  the 
  Trionyx 
  priscus 
  Leidy, 
  in 
  the 
  character 
  of 
  its 
  sculpture. 
  It 
  is 
  pitted 
  coarsely 
  and 
  

   regularly, 
  five 
  to 
  six 
  in 
  an 
  inch 
  on 
  a 
  costal 
  or 
  vertebral 
  plate. 
  In 
  the 
  Tr. 
  priscus 
  the 
  pits 
  are 
  considerably 
  smaller, 
  

   and 
  disposed 
  in 
  series 
  across 
  the 
  costal 
  plates, 
  which 
  are 
  separated 
  by 
  ridges 
  stronger 
  and 
  more 
  elevated 
  than 
  those 
  

   that 
  separate 
  the 
  pits 
  themselves. 
  The 
  same 
  arrangement 
  is 
  visible 
  on 
  a 
  portion 
  of 
  a 
  xiphisternal 
  bone, 
  from 
  green 
  

   sand, 
  near 
  Petersburg, 
  Ya., 
  in 
  the 
  collection 
  of 
  John 
  S. 
  Haines, 
  member 
  of 
  the 
  Academy, 
  with 
  portions 
  of 
  costal 
  

   plates, 
  all 
  referable 
  to 
  the 
  Tr. 
  prisons. 
  The 
  specimen 
  described 
  by 
  Leidy 
  was 
  from 
  Monmouth 
  Co., 
  N. 
  J. 
  The 
  con- 
  

   fluence 
  of 
  several 
  of 
  the 
  pits 
  produces 
  a 
  somewhat 
  similar 
  appearance, 
  as 
  is 
  common 
  among 
  Trionyches, 
  on 
  the 
  outer 
  

   margin 
  of 
  the 
  second 
  costal 
  plate 
  from 
  the 
  front 
  on 
  the 
  left 
  side, 
  and 
  probably 
  on 
  the 
  extremities 
  of 
  the 
  other 
  plates, 
  

   none 
  of 
  which 
  are 
  preserved. 
  On 
  a 
  portion 
  of 
  a 
  sternal 
  plate, 
  probably 
  xiphisternal, 
  the 
  pits 
  are 
  equal 
  and 
  regularly 
  

   distributed, 
  but 
  much 
  smaller 
  than 
  on 
  a 
  costal, 
  to 
  the 
  number 
  of 
  ten 
  in 
  an 
  inch. 
  

  

  One 
  costal 
  bears 
  a 
  portion 
  of 
  the 
  head 
  of 
  the 
  rib; 
  one 
  vertebral 
  a 
  nearly 
  complete 
  centrum 
  and 
  neural 
  arch, 
  and 
  

   another, 
  pleurapophyses. 
  Of 
  a 
  perfect 
  vertebral 
  plate 
  the 
  length 
  and 
  width 
  are 
  equal; 
  the 
  anterior 
  suture 
  concave, 
  

   the 
  posterior 
  convex. 
  The 
  costal 
  segments 
  are 
  markedly 
  curved. 
  The 
  following 
  measurements 
  will 
  furnish 
  further 
  

   characters. 
  

  

  