﻿CLASSIFICATION, 
  ETC. 
  OP 
  HAMILTON 
  AND 
  CHEMUNG 
  SERIES 
  323 
  

  

  Williams 
  in 
  case 
  its 
  identity 
  with 
  Newberry's 
  species 
  should 
  be 
  

   ultimately 
  disproved. 
  He 
  also 
  cites 
  the 
  discovery 
  by 
  Dr 
  J. 
  M. 
  

   Clarke 
  of 
  "the 
  anterior 
  extremity 
  of 
  a 
  mandible 
  of 
  Rhynckodus; 
  " 
  6 
  

   identified 
  by 
  Dr 
  Newberry. 
  

  

  A 
  second 
  Chemung 
  specimen 
  representing 
  the 
  lower 
  dorsal 
  plate 
  

   of 
  an 
  undescribed 
  species 
  of 
  Rhynchodus 
  is 
  preserved 
  in 
  the 
  Cam- 
  

   bridge 
  museum. 
  

  

  The 
  Chemung 
  of 
  northern 
  and 
  western 
  Pennsylvania 
  is 
  much 
  

   richer 
  in 
  fish-remains 
  than 
  New 
  York 
  state. 
  

  

  FISH-FAUNA 
  OF 
  THE 
  CATSKILL 
  FORMATION 
  

   Family 
  Ichthyodorulites 
  

  

  Genus 
  onchus 
  

   Onchus 
  rectus 
  sp. 
  nov. 
  

   A 
  new 
  species 
  of 
  selachian 
  fin-spines 
  is 
  apparently 
  represented 
  

   by 
  two 
  specimens 
  in 
  the 
  collection, 
  the 
  most 
  perfect 
  of 
  which 
  is 
  

   shown 
  in 
  the 
  annexed 
  figure. 
  This 
  is 
  5 
  cm 
  long, 
  and 
  .4 
  cm 
  in 
  

   maximum 
  width; 
  it 
  is 
  straight, 
  as 
  indicated 
  by 
  the 
  name, 
  and 
  

   tapers 
  gradually 
  to 
  an 
  acute 
  point. 
  The 
  inserted 
  portion 
  is 
  round 
  

   in 
  section, 
  and 
  covered 
  with 
  almost 
  microscopic 
  longitudinal 
  

   striae; 
  the 
  exserted 
  portion 
  on 
  the 
  other 
  hand 
  is 
  laterally 
  com- 
  

   pressed, 
  being 
  less 
  than 
  .2 
  cm 
  in 
  thickness. 
  The 
  anterior 
  mar- 
  

   gin 
  is 
  evenly 
  rounded, 
  and 
  very 
  delicately 
  striated. 
  The 
  lateral 
  

   face 
  is 
  traversed 
  by 
  a 
  number 
  of 
  fine 
  longitudinal 
  ridges, 
  as 
  many 
  

   as 
  10 
  being 
  counted 
  in 
  the 
  widest 
  portion. 
  These 
  are 
  non- 
  

   bifurcating, 
  and 
  are 
  all 
  of 
  uniform 
  size 
  and 
  regularly 
  spaced 
  with 
  

   the 
  exception 
  of 
  the 
  anterior 
  one, 
  which 
  is 
  twice 
  the 
  width 
  of 
  the 
  

   ochers, 
  and 
  is 
  round 
  in 
  section, 
  while 
  the 
  rest 
  are 
  triangular. 
  

  

  Fig. 
  4. 
  Onchus 
  rectus, 
  sp. 
  nov. 
  Dorsal 
  fin-spine. 
  

  

  Fine 
  striae 
  are 
  observable 
  with 
  a 
  lens 
  along 
  the 
  sides 
  of 
  the 
  

   costae. 
  The 
  latter 
  have 
  their 
  origin 
  along 
  a 
  slightly 
  oblique 
  line 
  

  

  a 
  Williams, 
  H. 
  S., 
  loc. 
  cit. 
  (1887) 
  p. 
  62, 
  63, 
  pi. 
  3, 
  fig. 
  1, 
  2. 
  

  

  6 
  Idem. 
  On 
  a 
  remarkable 
  fauna 
  at 
  the 
  base 
  of 
  the 
  Chemung 
  (Amer. 
  journ. 
  sci. 
  [3] 
  

   383. 
  25:98). 
  

  

  