﻿CLASSIFICATION, 
  ETC. 
  OF 
  HAMILTON 
  AND 
  CHEMUNG 
  SERIES 
  321 
  

  

  been 
  identical 
  with 
  some 
  of 
  the 
  forms 
  described 
  by 
  Newberry 
  in 
  

   1889 
  from 
  the 
  Chemung 
  of 
  Pennsylvania. 
  A 
  scale 
  belonging 
  to 
  

   an 
  undetermined 
  species 
  of 
  HoloptycMus 
  is 
  also 
  mentioned 
  by 
  

   H. 
  S. 
  Williams 
  a 
  as 
  occurring 
  in 
  the 
  Chemung 
  sandstone 
  of 
  Wells- 
  

   ville, 
  Allegany 
  co., 
  New 
  York. 
  H. 
  americanus 
  has 
  not 
  been 
  

   hitherto 
  reported 
  from 
  a 
  lower 
  horizon 
  than 
  the 
  Catskill, 
  hence 
  

   Proi 
  Prosser's 
  discovery 
  of 
  a 
  scale 
  in 
  the 
  Ithaca 
  beds 
  extends 
  the 
  

   range 
  of 
  this 
  species 
  a 
  considerable 
  distance 
  backward. 
  Pre- 
  

   vious 
  to 
  this 
  the 
  only 
  other 
  fish-remains 
  yielded 
  by 
  the 
  Ithaca 
  

   group 
  are 
  the 
  doubtfully 
  determinable 
  jaw 
  described 
  by 
  Prof. 
  Wil- 
  

   liams 
  6 
  a 
  few 
  years 
  ago 
  as 
  Dipterus 
  ithacensis, 
  and 
  a 
  supposed 
  

   Dinichthyid 
  fragment. 
  

  

  Holoptychius 
  americanus 
  Leidy 
  

  

  An 
  impression 
  of 
  the 
  outer 
  surface 
  of 
  a 
  scale 
  obtained 
  from 
  the 
  

   Ithaca 
  formation 
  at 
  Jefferson 
  shows 
  the 
  characteristic 
  markings 
  

   of 
  this 
  species. 
  The 
  scale 
  is 
  cycloidal, 
  measures 
  nearly 
  2 
  cm 
  in 
  

   diameter, 
  and 
  is 
  traversed 
  by 
  moderate-sized 
  inosculating 
  ridges 
  

   which 
  are 
  not 
  broken 
  up 
  into 
  tubercles. 
  It 
  was 
  possible 
  to 
  take 
  

   a 
  very 
  clear 
  reverse 
  impression 
  in 
  wax, 
  which 
  facilitated 
  the 
  

   determination. 
  

  

  Locality; 
  south 
  of 
  Jefferson, 
  Delaware 
  co. 
  

  

  Family 
  Onychodontidae 
  

   Genus 
  onychodus 
  

   Onychodus 
  sigmoides 
  Newberry 
  

   This 
  species, 
  like 
  Dinichthys 
  tuoerculatus 
  ranges 
  from 
  the 
  Cor- 
  

   niferous 
  to 
  the 
  Chemung, 
  but 
  teeth 
  occurring 
  in 
  the 
  latter 
  horizon 
  

   were 
  regarded 
  by 
  Newberry 
  as 
  constituting 
  a 
  separate 
  species 
  

   (0. 
  hopkinsi), 
  distinguished 
  by 
  its 
  somewhat 
  smaller 
  size. 
  The 
  

   average 
  hight 
  of 
  the 
  Chemung 
  teeth 
  is 
  about 
  3 
  cm, 
  but 
  gradations 
  

   occur 
  all 
  the 
  way 
  up 
  to 
  6 
  cm, 
  and 
  it 
  is 
  doubtful 
  if 
  this 
  size 
  is 
  

   exceeded 
  by 
  any 
  of 
  the 
  Corniferous 
  examples. 
  None 
  of 
  the 
  Che- 
  

   mung 
  teeth 
  were 
  figured 
  by 
  Newberry, 
  but 
  he 
  thus 
  summarizes 
  

   their 
  salient 
  characters 
  : 
  " 
  Teeth 
  generally 
  about 
  1 
  inch 
  in 
  length, 
  

  

  a 
  Williams, 
  H. 
  S. 
  On 
  the 
  fossil 
  faunas 
  of 
  the 
  Upper 
  Devonian 
  (Bull. 
  U. 
  S. 
  geol. 
  survey, 
  1887, 
  no. 
  4, 
  

   p. 
  78). 
  

   b 
  Proc. 
  Amer. 
  ass'n 
  adv. 
  sci. 
  1881, 
  30: 
  193. 
  

  

  