﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  

  

  205 
  

  

  Distinguishing 
  characters. 
  Subcircular; 
  gibbous; 
  strongly 
  con- 
  

   vex 
  pedicle 
  valve 
  with 
  deep 
  median 
  fur- 
  

   row, 
  deepening 
  and 
  widening 
  forward; 
  

   frontal 
  linguiform 
  elevation, 
  obtuse 
  cari 
  

   nated 
  fold 
  in 
  sinus; 
  strong 
  fold 
  on 
  brachial 
  

   valve, 
  with 
  a 
  lateral 
  fold 
  on 
  each 
  side 
  more 
  

   or 
  less 
  prominent. 
  

  

  Fig. 
  121 
  Hyattella 
  congests 
  

  

  Fig. 
  131a 
  Hyattella 
  congesta 
  

  

  Found 
  in 
  the 
  lower 
  Clinton 
  limestone 
  at 
  Niagara. 
  Also 
  at 
  Lock- 
  

   port 
  (Hall). 
  

  

  Genus 
  anoplotheca 
  Sandberger 
  

  

  [Ety. 
  : 
  avo-Xo^, 
  unarmed; 
  O-^xr/, 
  sheath] 
  

  

  (1853. 
  Sit^b. 
  d. 
  K. 
  K. 
  Akad. 
  d. 
  IVisscns. 
  math, 
  naturw. 
  Classe, 
  

   16, 
  p. 
  5, 
  18, 
  102; 
  1894. 
  Hall 
  & 
  Clarke. 
  Pal. 
  N. 
  Y. 
  v. 
  8, 
  pt 
  2, 
  p. 
  129) 
  

  

  Concavo-convex, 
  small 
  shells 
  with 
  few 
  plications 
  crossed 
  by 
  fine 
  

   often 
  imbricating 
  growth 
  lines. 
  Brachial 
  valve 
  with 
  a 
  high 
  median 
  

   septum. 
  Brachidium 
  a 
  pair 
  of 
  spiral 
  cones, 
  as 
  in 
  W 
  h 
  i 
  t 
  - 
  

   f 
  i 
  e 
  1 
  d 
  e 
  1 
  1 
  a 
  . 
  

  

  Anoplotheca 
  hemispherica 
  (Sowerby) 
  

   (Fig. 
  132). 
  Atrypa 
  hemispherica 
  

   Hall 
  (1852. 
  Pal. 
  N. 
  Y. 
  2.74, 
  pi. 
  23) 
  

  

  Distinguishing 
  characters. 
  Hemispheric 
  

   to 
  semiorbicular 
  form; 
  nearly 
  flat 
  brachial 
  

   valve, 
  convex 
  pedicle 
  valve; 
  extended, 
  

   nearly 
  straig^ht 
  hing-e 
  line; 
  eight 
  to 
  12 
  

  

  Fig. 
  132 
  Anoplotheca 
  hemispherica 
  .^ 
  te 
  te 
  > 
  fe 
  

  

  With 
  striae 
  enlarged 
  rouudcd 
  to 
  subaugular, 
  simple 
  plications; 
  

  

  strong, 
  undulating 
  concentric 
  striae. 
  

  

  Found 
  poorly 
  preserved 
  in 
  the 
  Clinton 
  shale 
  at 
  Niagara. 
  

  

  Anoplotheca 
  plicatula 
  (Hall) 
  (Fig. 
  133). 
  Atrypa 
  plicatula 
  

   Hall 
  (1852. 
  Pal. 
  N. 
  Y. 
  2:74, 
  pi. 
  23) 
  

  

  Distinguishing 
  characters. 
  Slightly 
  wider 
  than 
  long 
  or 
  sub- 
  

  

  