﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  

  

  217 
  

  

  Gomphoceras 
  ? 
  sp. 
  (Hall. 
  1852. 
  Pal 
  N. 
  Y. 
  2:290, 
  pi. 
  61) 
  

   Distinguishing 
  characters. 
  Subfusiform 
  aperture 
  narrowed, 
  grad- 
  

   ually 
  tapering 
  to 
  the 
  extremity 
  ; 
  surface 
  striated 
  transversely. 
  

  

  This 
  fossil 
  has 
  the 
  general 
  form 
  and 
  appearance 
  of 
  Gompho- 
  

   ceras, 
  though 
  I 
  am 
  unable 
  to 
  discover 
  any 
  marks 
  of 
  septa. 
  The 
  

   greatest 
  expansion 
  appears 
  to 
  be 
  at 
  about 
  one 
  third 
  of 
  the 
  distance 
  

   from 
  the 
  aperture 
  to 
  the 
  apex. 
  

  

  Found 
  " 
  in 
  a 
  fragment 
  of 
  limestone 
  below 
  the 
  clifif 
  at 
  Niagara 
  

   Falls 
  " 
  (Hall). 
  

  

  Fig. 
  149 
  Trochoceras 
  gebhardi, 
  two 
  thirds 
  natural 
  size 
  

  

  Genus 
  trochoceras 
  Hall 
  

  

  [Ety. 
  : 
  rpoxo?, 
  a 
  wheel; 
  xipa?, 
  a 
  horn 
  (named 
  from 
  its 
  trochus 
  

   or 
  top-like 
  shape)] 
  

  

  (1852. 
  PaLN..Y.2:sss) 
  

  

  Shells 
  turbinate 
  or 
  trochiform; 
  spire 
  elevated 
  as 
  in 
  Gastropoda, 
  

   'more 
  or 
  less 
  ventricose 
  and 
  umbilicated; 
  aperture 
  rounded 
  or 
  round 
  

   oval; 
  volutions 
  above 
  the 
  outer 
  one 
  with 
  septa; 
  siphuncle 
  sub- 
  

   marginal 
  or 
  dorsal. 
  

  

  Trochoceras 
  gebhardi 
  Hall 
  (Fig. 
  149) 
  (1852. 
  Pal. 
  AL 
  Y. 
  2:335, 
  

   pl- 
  77> 
  77^\ 
  Grabau. 
  Geol. 
  soc. 
  Am. 
  Bid. 
  11:371, 
  pi. 
  21) 
  

  

  Distinguishing 
  characters. 
  Deep 
  and 
  wide 
  umbilicus 
  with 
  angular 
  

   margins; 
  cross-section 
  of 
  body 
  whorl 
  irregularly 
  subhemispheric; 
  

  

  