﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  97 
  

  

  branching 
  seaweed, 
  Bythotrephis 
  gracilis, 
  may 
  be 
  found. 
  

   This 
  occurs 
  also 
  on 
  some 
  of 
  the 
  shaly 
  partings 
  of 
  the 
  limestones. 
  

   The 
  impressions 
  vary 
  from 
  the 
  slender 
  variety 
  of 
  great 
  delicacy 
  to 
  

   a 
  coarse 
  one 
  in 
  which 
  the 
  frond 
  consists 
  of 
  broad 
  irregular 
  lobes. 
  

  

  This 
  stratum 
  generally 
  forms 
  a 
  vertical 
  wall 
  with 
  the 
  next 
  over- 
  

   lying 
  stratum 
  projecting 
  beyond 
  it. 
  

  

  Clinton 
  upper 
  limestone. 
  In 
  the 
  region 
  of 
  the 
  Genesee 
  river 
  the 
  

   lower 
  limestone 
  is 
  succeeded 
  by 
  a 
  mass 
  of 
  shale 
  which 
  is 
  generally 
  

   fossiliferous, 
  and 
  on 
  which 
  lies 
  the 
  upper 
  limestone. 
  In 
  the 
  Niagara 
  

   region 
  this 
  shale 
  is 
  wholly 
  wanting, 
  the 
  upper 
  limestone 
  resting 
  

   directly 
  on 
  the 
  lower. 
  The 
  line 
  of 
  separation 
  is 
  however 
  well 
  

   marked, 
  both 
  by 
  the 
  diverse 
  characters 
  of 
  the 
  two 
  rocks 
  and 
  by 
  

   the 
  different 
  way 
  in 
  which 
  each 
  resists 
  destruction 
  by 
  atmospheric 
  

   agencies. 
  The 
  upper 
  stratum 
  is 
  a 
  crystalline 
  and 
  highly 
  fossiliferous 
  

   limestone, 
  often 
  pinkish 
  in 
  color, 
  though 
  chiefly 
  light 
  gray 
  with 
  

   yellowish 
  or 
  brownish 
  particles 
  where 
  oxidation 
  has 
  occurred. 
  

   Portions 
  of 
  the 
  beds 
  consist 
  almost 
  wholly 
  of 
  crinoid 
  stems 
  or 
  

   joints, 
  which 
  give 
  the 
  rock 
  a 
  coarsely 
  crystalline 
  and 
  sometimes 
  

   porous 
  aspect. 
  Fossils 
  are 
  abundant 
  in 
  this 
  rock, 
  though 
  the 
  

   variety 
  is 
  generally 
  not 
  large. 
  The 
  most 
  common 
  species 
  is 
  a 
  

   rotund 
  variety 
  of 
  the 
  brachiopod, 
  Atrypa 
  reticularis 
  (fig. 
  

   112), 
  which 
  is 
  generally 
  very 
  robust 
  and 
  sometimes 
  almost 
  globular 
  

   in 
  form. 
  Of 
  the 
  other 
  fossils 
  in 
  this 
  rock 
  several 
  Stropheodontas 
  

   may 
  be 
  mentioned, 
  among 
  them 
  Stropheodonta 
  pro- 
  

   funda. 
  A 
  number 
  of 
  rhynchonelloid 
  shells 
  occur, 
  readily 
  recog- 
  

   nized 
  by 
  their 
  pointed 
  beaks 
  and 
  strong 
  plications. 
  Among 
  these 
  

   are 
  some 
  small 
  specimens 
  of 
  Camarotoechia 
  acinus, 
  a 
  

   species 
  characteristic 
  of 
  the 
  Niagara 
  beds 
  of 
  the 
  west. 
  It 
  is 
  readily 
  

   recognized 
  by 
  its 
  smooth 
  umbonal 
  area, 
  and 
  its 
  single 
  plication 
  in 
  

   the 
  mesial 
  depression 
  or 
  sinus, 
  corresponding 
  to 
  which, 
  on 
  the 
  

   opposite 
  valve 
  occur 
  two 
  plications. 
  Among 
  the 
  more 
  abundant 
  

   fossils 
  of 
  this 
  rock 
  are 
  smooth 
  elongate 
  and 
  rather 
  strongly 
  biconvex 
  

   brachiopods 
  of 
  the 
  genus 
  Whitfieldella. 
  The 
  most 
  common 
  

   is 
  W. 
  intermedia^ 
  but 
  other 
  species 
  occur 
  as 
  well. 
  The 
  thick- 
  

   ness 
  of 
  this 
  stratum 
  is 
  ii 
  feet. 
  The 
  upper 
  beds 
  of 
  this 
  series 
  con- 
  

   tain 
  species 
  which 
  on 
  the 
  whole 
  are 
  of 
  a 
  strongly 
  marked 
  Niagaran 
  

  

  