﻿166 
  Twenty-eighth 
  Beport 
  on 
  the 
  State 
  Museum. 
  

   RHYNCHOTRETA 
  n. 
  gen. 
  

  

  Type, 
  Rhynchonella 
  cuneata 
  Daiman. 
  

  

  Shell 
  triangular, 
  surface 
  with 
  angular 
  plications. 
  Ventral 
  

   beak 
  straight, 
  produced 
  beyond 
  the 
  dorsal 
  beak, 
  extremity 
  

   perforate, 
  the 
  foramen 
  with 
  an 
  elevated 
  margin 
  ; 
  space 
  be- 
  

   tween 
  the 
  foramen 
  and 
  hinge-line 
  occupied 
  by 
  a 
  deltidium 
  in 
  

   two 
  pieces, 
  being 
  divided 
  by 
  a 
  longitudinal 
  suture, 
  and 
  trans- 
  

   versely 
  striated. 
  Yalves 
  articulated 
  by 
  two 
  slender 
  curving 
  

   teeth, 
  proceeding 
  from 
  a 
  broad 
  curving 
  hinge-plate 
  in 
  the 
  ven- 
  

   tral 
  valve, 
  which 
  fit 
  into 
  corresponding 
  sockets 
  in 
  the 
  dorsal 
  

   valve. 
  Crurse 
  rising 
  from 
  near 
  the 
  dorsal 
  beak, 
  and 
  curving 
  

   into 
  the 
  ventral 
  cavity, 
  and 
  thence 
  recurved 
  toward 
  the 
  dor- 
  

   sal 
  side, 
  and 
  probably 
  uniting, 
  as 
  shown 
  in 
  figure 
  4, 
  p. 
  167. 
  

   Structure 
  fibrous 
  and 
  apparently 
  very 
  minutely 
  punctate. 
  

  

  The 
  ffliynchonella 
  cuneata 
  of 
  Daiman 
  has 
  been 
  retainecL 
  

   under 
  that 
  genus 
  by 
  nearly 
  all 
  authors. 
  In 
  1859, 
  Salter 
  refer- 
  

   red 
  the 
  species 
  to 
  Retzia.* 
  An 
  examination 
  of 
  specimens 
  in 
  

   my 
  possession, 
  in 
  1863, 
  revealed 
  no 
  satisfactory 
  evidence 
  of 
  

   punctate 
  structure, 
  or 
  internal 
  crurse 
  or 
  spires 
  ; 
  and 
  I 
  still 
  

   continued 
  it 
  under 
  , 
  Rhynchonella. 
  The 
  collections 
  from 
  

   Waldron 
  have 
  shown 
  the 
  punctate 
  texture 
  of 
  the 
  shell, 
  and 
  

   the 
  existence 
  of 
  long 
  curving 
  crura, 
  which 
  are 
  unlike 
  any 
  fea- 
  

   ture 
  known 
  in 
  palaeozoic 
  Rhynchonella, 
  and 
  assimilate 
  this 
  

   fossil 
  to 
  the 
  Terebratulidse. 
  

  

  This 
  form 
  is 
  not 
  congeneric 
  with 
  Retzia 
  Adrieni, 
  and 
  can- 
  

   not 
  properly 
  be 
  referred 
  to 
  that 
  genus, 
  though 
  approaching 
  

   in 
  external 
  characters 
  to 
  M. 
  ferita, 
  which 
  is 
  represented 
  as 
  

   possessing 
  internal 
  spires. 
  It 
  becomes 
  necessary, 
  therefore, 
  

   to 
  characterize 
  it 
  as 
  a 
  distinct 
  genus, 
  for 
  which 
  I 
  have 
  pro- 
  

   posed 
  the 
  name 
  Rhynchotreta. 
  The 
  accompanying 
  figures 
  

   illustrate 
  its 
  principal 
  features. 
  

  

  * 
  Siluria, 
  2ud 
  Edition, 
  pi. 
  xxii, 
  fig. 
  8. 
  1859. 
  

  

  