﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  169 
  

  

  subangular, 
  becoming 
  depressed 
  and 
  sometimes 
  obsolete 
  on 
  

   the 
  cardinal 
  slopes, 
  usually 
  simple, 
  enlarging 
  toward 
  the 
  

   front 
  of 
  the 
  shell, 
  rarely 
  bifurcating 
  or 
  with 
  an 
  intercalated 
  

   oneon 
  the 
  middle 
  of 
  the 
  shell, 
  but 
  bifurcating 
  or 
  intercalating 
  

   in 
  a 
  remarkable 
  manner 
  on 
  the 
  sides, 
  where 
  the 
  folds 
  bend 
  

   abruptly 
  outwards 
  to 
  the 
  cardino-lateral 
  margins 
  ; 
  plications 
  

   crossed 
  by 
  arching 
  imbricating 
  striae 
  of 
  growth, 
  which 
  are 
  

   sometimes 
  very 
  conspicuous. 
  

  

  The 
  individuals 
  of 
  this 
  species 
  measure 
  from 
  11 
  to 
  17 
  mm. 
  

   in 
  length, 
  from 
  12 
  to 
  19 
  mm. 
  in 
  width, 
  and 
  9 
  to 
  12 
  mm. 
  in 
  

   depth. 
  

  

  This 
  form, 
  from 
  the 
  Waldron 
  locality, 
  diners 
  from 
  the 
  An- 
  

   astropMa 
  (Airy 
  pa) 
  interplicata, 
  ut 
  cit. 
  of 
  the 
  Niagara 
  

   group 
  of 
  New 
  York 
  in 
  its 
  larger 
  growth, 
  with 
  more 
  rounded 
  

   or 
  less 
  angular 
  plications, 
  and 
  in 
  being 
  almost 
  free 
  from 
  inter- 
  

   calated 
  plications, 
  which 
  are 
  constant 
  and 
  characteristic 
  in 
  

   that 
  species, 
  and 
  in 
  having 
  no 
  defined 
  mesial 
  6inus, 
  which 
  is 
  

   always 
  a 
  feature 
  in 
  the 
  New 
  York 
  form. 
  Similar 
  features 
  are 
  

   described 
  as 
  characteristic 
  of 
  A. 
  brevirostris, 
  of 
  which 
  I 
  have 
  

   no 
  good 
  specimens 
  before 
  me. 
  It 
  is 
  quite 
  probable 
  that 
  these 
  

   New 
  York 
  forms, 
  which 
  are 
  described 
  as 
  two 
  species, 
  are 
  in 
  

   reality 
  but 
  varieties 
  of 
  the 
  same. 
  

  

  Noting 
  these 
  differences 
  between 
  the 
  New 
  York 
  specimens 
  

   and 
  those 
  from 
  Waldron, 
  I 
  had 
  originally 
  (Transactions 
  

   Albany 
  Institute, 
  vol. 
  iv, 
  p. 
  227) 
  indicated 
  the 
  latter 
  as 
  more 
  

   nearly 
  approaching 
  to 
  A. 
  Vemeuili, 
  from 
  the 
  Lower 
  Helder- 
  

   berg 
  group 
  in 
  New 
  York. 
  They 
  however 
  present 
  several 
  

   marked 
  differences 
  ; 
  this 
  form 
  is 
  smaller, 
  more 
  rounded 
  and 
  

   less 
  ventricose 
  ; 
  the 
  umbonesless 
  prominent 
  and 
  not 
  so 
  closely 
  

   incurved 
  ; 
  the 
  sinus 
  rounded 
  and 
  undefined, 
  never 
  deep 
  nor 
  

   angular 
  ; 
  the 
  plications 
  more 
  rounded, 
  generally 
  continuous 
  

   to 
  the 
  beaks, 
  and 
  occasionally 
  increasing 
  by 
  implantation 
  or 
  

   bifurcation, 
  while 
  the 
  latter 
  is 
  a 
  constant 
  character 
  in 
  A. 
  Ver- 
  

   neuili. 
  

  

  EICHWALDIA 
  Billings. 
  

   Eichwaldia 
  reticulata. 
  

  

  Plate 
  26, 
  Figs. 
  50-54. 
  

  

  Rhynchonella 
  reticulata? 
  Hall. 
  Trans. 
  Alb. 
  Inst., 
  vol. 
  iv, 
  p. 
  217. 
  Abstract, 
  p. 
  

  

  23; 
  May, 
  1863. 
  

   Eichwaldia 
  reticulata 
  Hall. 
  20th 
  Rept. 
  St. 
  Cab., 
  Nat. 
  Hist., 
  p. 
  275. 
  1867. 
  

  

  Shell 
  varying 
  from 
  elongate-triangular 
  to 
  transversely 
  

  

  