﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  173 
  

  

  Modiolopsis 
  subalatus. 
  

  

  Plate 
  27, 
  Figs. 
  6, 
  6. 
  

   Modiolopsis 
  subalatus 
  Hall.. 
  Pal. 
  N. 
  Y., 
  vol. 
  ii, 
  p. 
  84, 
  pi. 
  27, 
  figs. 
  5 
  and 
  6. 
  1852. 
  

  

  Shell 
  rhomboidal 
  ovate, 
  the 
  proportions 
  of 
  length 
  and 
  

   breadth 
  varying 
  in 
  different 
  individuals, 
  one 
  of 
  the 
  specimens 
  

   figured 
  having 
  a 
  length 
  once 
  and 
  three- 
  fourths 
  as 
  great 
  as 
  the 
  

   width, 
  while 
  the 
  other 
  is 
  less 
  than 
  once 
  and 
  a 
  half 
  as 
  long 
  as 
  

   wide. 
  Hinge-line 
  equaling 
  or 
  greater 
  than 
  one-half 
  the 
  length 
  

   of 
  the 
  shell 
  ; 
  umbo 
  prominent, 
  beak 
  moderately 
  elevated 
  above 
  

   the 
  cardinal 
  line 
  ; 
  posterior 
  side 
  broadly 
  rounded 
  and 
  sub- 
  

   alate 
  above 
  ; 
  anterior 
  side 
  narrow, 
  rounded 
  or 
  subacute 
  ; 
  basal 
  

   margin 
  anterior 
  to 
  the 
  center, 
  and 
  nearly 
  beneath 
  the 
  beak, 
  

   more 
  or 
  less 
  distinctly 
  arcuate. 
  Surface 
  marked 
  by 
  fine 
  con- 
  

   centric 
  lines 
  of 
  growth. 
  

  

  Length 
  of 
  shell 
  31 
  to 
  37 
  mm. 
  ; 
  greatest 
  width 
  22 
  to 
  23 
  mm. 
  

  

  The 
  specimens 
  from 
  Waldron 
  are 
  much 
  larger 
  than 
  those 
  

   known 
  in 
  New 
  York, 
  but 
  they 
  are 
  in 
  other 
  respects 
  similar. 
  

   Without 
  a 
  greater 
  amount 
  of 
  material 
  for 
  comparison, 
  I 
  do 
  

   not 
  feel 
  warranted 
  in 
  making 
  any 
  specific 
  distinction. 
  

  

  PTERINEA 
  Ooldfuss. 
  

   Pterinea 
  brisa. 
  

  

  Plate 
  27, 
  Figs. 
  7-9. 
  

  

  Pterinea 
  brisa 
  Hall. 
  20th 
  Rep. 
  St. 
  Cab. 
  Nat. 
  Hist., 
  p. 
  337, 
  pi. 
  14, 
  fig. 
  1. 
  1867. 
  

  

  Rev. 
  Edit., 
  p. 
  384. 
  1870. 
  

   Compare 
  Avicula 
  emacerata 
  Conr. 
  Hall. 
  Pal. 
  N. 
  Y., 
  vol. 
  ii, 
  p. 
  282, 
  pi. 
  69, 
  figs. 
  

  

  lo-le. 
  1852. 
  

   Compare 
  Ambonychia 
  (Pterinea) 
  strioecostata 
  McChesney. 
  New 
  Pal. 
  Foss., 
  p. 
  88, 
  

  

  pi. 
  9, 
  fig. 
  4; 
  and 
  Trans. 
  Chio. 
  Aoad. 
  Soi., 
  vol. 
  i, 
  p. 
  88, 
  pi. 
  9, 
  fig. 
  4. 
  1869. 
  

  

  Body 
  of 
  shell 
  (left 
  valve) 
  obliquely 
  sub 
  ovate, 
  extremely 
  in- 
  

   equilateral 
  ; 
  anterior 
  wing 
  moderately 
  extended 
  and 
  strongly 
  

   sinuate 
  at 
  its 
  junction 
  with 
  the 
  body 
  ; 
  posterior 
  wing 
  not 
  ex- 
  

   tending 
  as 
  far 
  as 
  the 
  posterior 
  extremity 
  of 
  the 
  shell 
  ; 
  umbo 
  

   prominent, 
  beak 
  rising 
  a 
  little 
  above 
  the 
  hinge-line 
  ; 
  musculfar 
  

   impression 
  in 
  right 
  valve 
  large 
  and 
  nearly 
  round, 
  near 
  the 
  

   middle 
  of 
  the 
  length 
  of 
  the 
  shell. 
  In 
  the 
  casts, 
  beneath 
  or 
  

   just 
  anterior 
  to 
  the 
  beak, 
  there 
  is 
  one 
  short 
  curving 
  dental 
  

  

  