﻿192 
  

  

  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Genus 
  rhynchotreta 
  Hall 
  

   [Ety.: 
  puyxo?, 
  beak; 
  rprjrd, 
  with 
  a 
  hole] 
  

  

  (1879. 
  ^' 
  ^' 
  ^^^^^ 
  ^^^^^•^- 
  ^^^- 
  ^^^^- 
  ^8^^ 
  ^^' 
  ^ep't, 
  P- 
  166; 
  1893. 
  

   Pal 
  N. 
  Y. 
  V. 
  8, 
  pt 
  2, 
  p. 
  185) 
  

  

  Shell 
  triangular; 
  surface 
  with 
  angular 
  plications. 
  Beak 
  of 
  pedicle 
  

   valve 
  straight, 
  produced 
  beyond 
  that 
  of 
  the 
  opposite 
  valve, 
  extremity 
  

   perforate, 
  the 
  foramen 
  with 
  an 
  elevated 
  margin. 
  Two 
  longitudinally 
  

   striated 
  deltidial 
  plates 
  fill 
  the 
  delthyrium. 
  Teeth 
  slender, 
  curving, 
  

   proceeding 
  from 
  a 
  broad 
  curving 
  hinge 
  plate 
  in 
  the 
  pedicle 
  valve. 
  

   Brachidium 
  a 
  slightly 
  modified 
  loop. 
  

  

  Ehynchotreta 
  cuneata 
  var. 
  americana 
  Hall 
  (Fig. 
  105). 
  

   Atrypa 
  cuneata 
  Hall 
  (1852. 
  Pal. 
  N. 
  Y. 
  2:276, 
  pi. 
  57, 
  

  

  fig. 
  4a-r) 
  

  

  Distinguishing 
  characters. 
  Triangu- 
  

   lar 
  and 
  cuneiform 
  outline; 
  longer 
  

   than 
  wide; 
  elongate 
  angular 
  beak 
  

   of 
  pedicle 
  valve 
  with 
  compressed, 
  

   fiat 
  or 
  concave 
  sides; 
  wide, 
  deep 
  sinus 
  

   in 
  adult, 
  extending 
  two 
  thirds 
  to 
  the 
  

   beak; 
  profound 
  frontal 
  emargination 
  ; 
  

   strong 
  angular 
  plications, 
  three 
  in 
  

   sinus, 
  four 
  on 
  fold, 
  the 
  two 
  central 
  ones 
  

  

  most 
  prominent; 
  numerous 
  regular, 
  fine 
  thread-like 
  concentric 
  

  

  striae; 
  minutely 
  papillose 
  surface. 
  

  

  Found 
  in 
  the 
  CHnton 
  lenses 
  and 
  the 
  lower 
  Rochester 
  shale 
  and 
  

  

  particularly 
  in 
  the 
  Bryozoa 
  beds, 
  where 
  it 
  is 
  abundant; 
  rarely 
  above 
  

  

  this. 
  Niagara 
  sections. 
  Also 
  at 
  Lockport 
  and 
  elsewhere 
  (Hall). 
  

  

  Fig. 
  105 
  Rhynchotreta 
  cuneata 
  var 
  

   americana 
  

  

  Genus 
  camarotoechia 
  Hall 
  & 
  Clarke 
  

  

  [Ety.: 
  xa/j.dpa, 
  arched 
  chamber; 
  rolxo?, 
  partition] 
  

  

  (1893. 
  Pal. 
  N. 
  Y. 
  V. 
  8, 
  pt 
  2, 
  p. 
  189) 
  

  

  Shell 
  rhynchonehoid, 
  trihedral 
  in 
  contour, 
  with 
  shallow 
  pedicle 
  

   and 
  convex 
  brachial 
  valve; 
  no 
  hinge 
  area; 
  beak 
  of 
  pedicle 
  valve 
  

   projecting 
  and 
  incurved. 
  Surface 
  radially 
  plicate, 
  sinus 
  and 
  fold 
  in 
  

   pedicle 
  and 
  brachial 
  valves 
  respectively. 
  Distinctive 
  internal 
  char- 
  

   acters 
  (separating 
  this 
  genus 
  from 
  other 
  " 
  Rhynchonellas 
  ") 
  are: 
  a 
  

  

  