﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  171 
  

  

  LAMELLIBRANCHIATA. 
  

  

  AMPHICCELIA 
  Hall. 
  

  

  Amphiccelia 
  Leidyi. 
  

  

  Plate 
  27, 
  Fig. 
  1 
  and 
  Fig. 
  2?. 
  

  

  Amphiccelia 
  Leidyi 
  Hall. 
  20th 
  Rep. 
  St. 
  Cab. 
  Nat. 
  Hist., 
  p. 
  339, 
  pi. 
  14. 
  figs. 
  13-15. 
  

   Rev. 
  Edit., 
  p. 
  387. 
  

  

  The 
  specimens 
  from 
  Waldron, 
  which 
  I 
  have 
  referred 
  to 
  this 
  

   species, 
  are 
  in 
  the 
  condition 
  of 
  casts 
  of 
  the 
  interior, 
  and 
  are 
  

   more 
  or 
  less 
  flattened 
  in 
  the 
  soft 
  shales. 
  The 
  fossil 
  preserves 
  

   the 
  usual 
  rhomboidal 
  form 
  of 
  the 
  species 
  ; 
  the 
  beak 
  is 
  much 
  

   elevated, 
  and 
  this 
  feature, 
  in 
  the 
  specimen 
  fig. 
  1, 
  is 
  apparently 
  

   increased 
  by 
  the 
  pressure 
  to 
  which 
  the 
  shell 
  has 
  been 
  sub- 
  

   jected. 
  The 
  hinge-line 
  is 
  more 
  oblique 
  than 
  in 
  the 
  typical 
  

   iorms 
  of 
  the 
  species, 
  but 
  this 
  may 
  be 
  due 
  to 
  pressure. 
  

  

  The 
  casts 
  preserve 
  some 
  remains 
  of 
  concentric 
  striae, 
  but 
  

   there 
  is 
  no 
  evidence 
  of 
  the 
  fine 
  radiating 
  strise 
  which 
  are 
  

   characteristic 
  of 
  the 
  genus. 
  The 
  length 
  of 
  the 
  shell 
  is 
  equal 
  

   to 
  the 
  height, 
  as 
  shown 
  in 
  specimens 
  from 
  other 
  localities. 
  

  

  The 
  specimen 
  fig. 
  2, 
  has 
  a 
  length 
  greater 
  than 
  the 
  height, 
  

   the 
  beak 
  is 
  less 
  elevated 
  and 
  at 
  a 
  greater 
  distance 
  from 
  the 
  

   anterior 
  margin, 
  giving 
  a 
  more 
  equilateral 
  aspect 
  to 
  the 
  fossil. 
  

   This 
  may 
  be 
  a 
  distinct 
  species, 
  but 
  owing 
  to 
  the 
  condition 
  in 
  

   which 
  the 
  specimens 
  occur, 
  it 
  would 
  be 
  impossible 
  to 
  indicate 
  

   specific 
  characters 
  beyond 
  the 
  general 
  form 
  of 
  the 
  shell. 
  

  

  Almost 
  all 
  the 
  specimens 
  of 
  Lamellibranchiata 
  from 
  the 
  

   Waldron 
  locality 
  are 
  in 
  the 
  condition 
  of 
  casts 
  of 
  the 
  interior, 
  

   the 
  shell 
  having 
  been 
  dissolved, 
  while 
  the 
  shaly 
  material, 
  with 
  

   which 
  it 
  was 
  filled, 
  preserves 
  the 
  characters 
  in 
  a 
  very 
  imper- 
  

   fect 
  manner. 
  

  

  Ambonychia 
  aoutirostra. 
  

  

  Plate 
  7, 
  fig. 
  12. 
  

   Ambonychia 
  acutirostra 
  Hall. 
  20th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist., 
  p. 
  336, 
  pi. 
  14, 
  flg. 
  

  

  2. 
  1867; 
  Rev. 
  Edit., 
  p. 
  383. 
  

   Ambonyehia 
  acutirostra 
  Hall. 
  Under 
  reference 
  to 
  Sagenella 
  elegans. 
  Doo. 
  

  

  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Explanation 
  of 
  pi. 
  7, 
  fig. 
  12. 
  1876. 
  

  

  Shell 
  narrow 
  ovate, 
  subequilateral, 
  length 
  nearly 
  twice 
  the 
  

   width 
  ; 
  valves 
  moderately 
  convex, 
  sloping 
  very 
  abruptly 
  to 
  

  

  