﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  

  

  131 
  

  

  These 
  organisms 
  occur 
  as 
  mere 
  impressions 
  on 
  the 
  rock 
  surfaces, 
  

   varying 
  in 
  slenderness 
  of 
  branches 
  from 
  less 
  than 
  i 
  mm 
  to 
  5 
  mm 
  

   (varieties 
  intermedia 
  and 
  c 
  r 
  a 
  s 
  s 
  a). 
  

  

  Fig. 
  25 
  Bythotrephis 
  gracilis 
  ; 
  showing 
  varieties. 
  

   e 
  B. 
  gracilis 
  var. 
  crassa 
  

  

  a 
  B. 
  gracilis; 
  h 
  B. 
  gracilis 
  var. 
  intermedia; 
  

  

  Found 
  in 
  the 
  shaly 
  partings 
  separating 
  the 
  thin 
  beds 
  of 
  the 
  lower 
  

   Clinton 
  limestone 
  at 
  Niagara. 
  

  

  Bythotrephis 
  lesquereuxi 
  

   Grote 
  & 
  Pitt 
  (Fig. 
  26) 
  

   (1876. 
  Bitifalo 
  soc. 
  nat. 
  

   sci. 
  Bui. 
  3:88, 
  4:20, 
  fig. 
  6) 
  

  

  Distinguishing 
  characters. 
  

   Flattened, 
  erect 
  stem; 
  sim- 
  

   ple, 
  sparingly 
  dichotomous 
  

   branches, 
  3-4 
  mm 
  thick, 
  

   gradually 
  widening 
  to 
  near- 
  

   ly 
  I 
  cm 
  at 
  the 
  very 
  obtuse 
  

   or 
  round 
  truncate 
  point; 
  ^. 
  „, 
  .^ 
  ,, 
  . 
  ^. 
  , 
  

  

  1 
  ^ 
  ' 
  Fig. 
  CG 
  rytliotrephis 
  lesquorcuxi 
  

  

  