﻿The 
  Fauna 
  oe 
  the 
  Niagara 
  Group. 
  155 
  

  

  CHONETES 
  Fischer. 
  

   Chonetes 
  ISTova-Scotica. 
  

  

  Plate 
  22, 
  Figs. 
  11-14. 
  

  

  Chonetes 
  Nova-Scotica 
  Hall. 
  Silurian 
  and 
  Devonian 
  Rocks 
  of 
  Nova 
  Scotia, 
  by 
  

  

  J. 
  W. 
  Dawson, 
  p. 
  13. 
  1860. 
  

   Chonetes 
  Nova-Scotica 
  Hall. 
  Canadian 
  Nat. 
  and 
  Geologist, 
  vol. 
  v, 
  no. 
  2, 
  p. 
  144. 
  

  

  1860. 
  

  

  Shell 
  semi 
  elliptical, 
  width 
  varying 
  from 
  once 
  and 
  a 
  half 
  to 
  

   nearly 
  twice 
  the 
  length, 
  greatest 
  width 
  near 
  the 
  middle. 
  Ven- 
  

   tral 
  valve 
  variably 
  convex, 
  and 
  often 
  showing 
  a 
  flattened 
  or 
  

   slightly 
  concave 
  space 
  down 
  the 
  middle 
  of 
  the 
  shell, 
  with 
  oc- 
  

   casionally 
  a 
  stronger 
  and 
  more 
  elevated 
  ray 
  along 
  the 
  median 
  

   line, 
  from 
  beak 
  to 
  base 
  of 
  the 
  ventral 
  valve; 
  cardinal 
  margin 
  or- 
  

   namented 
  by 
  from 
  two 
  to 
  five 
  slender 
  spines 
  on 
  each 
  side 
  of 
  the 
  

   beak 
  ; 
  cardino-lateral 
  margins 
  often 
  a 
  little 
  wrinkled. 
  Dorsal 
  

   valve 
  moderately 
  concave. 
  Surface 
  finely 
  striated, 
  striae 
  flex- 
  

   nous, 
  dichotomizing 
  and 
  increasing 
  by 
  interstitial 
  addition 
  so 
  

   that 
  there 
  are 
  more 
  than 
  one 
  hundred 
  on 
  the 
  margin 
  of 
  the 
  

   shell, 
  stronger 
  below 
  the 
  umbo 
  ; 
  concentric 
  striae 
  tine, 
  close, 
  

   rounded 
  and 
  slightly 
  undulating. 
  

  

  This 
  species 
  resembles 
  in 
  form 
  the 
  Chonetes 
  cornuta 
  of 
  the 
  

   Clinton 
  group 
  of 
  New 
  York, 
  but 
  is 
  a 
  larger 
  and 
  more 
  ventri- 
  

   cose 
  shell 
  ; 
  the 
  striae 
  are 
  proportionally 
  less 
  numerous 
  and 
  

   more 
  closely 
  arranged, 
  the 
  interstices 
  being 
  less 
  than 
  the 
  striae, 
  

   while 
  in 
  C. 
  cornuta 
  the 
  interstices 
  are 
  wider 
  than 
  the 
  striae, 
  

   and 
  the 
  latter 
  increase 
  only 
  by 
  interstitial 
  additions 
  below 
  the 
  

   middle 
  of 
  the 
  shell. 
  

  

  All 
  the 
  specimens 
  from 
  Waldron 
  belong 
  to 
  the 
  variety 
  with 
  

   a 
  strong 
  median 
  ray 
  on 
  the 
  ventral 
  valve. 
  One 
  specimen 
  ob- 
  

   served 
  has 
  a 
  width 
  of 
  16 
  mm. 
  — 
  considerably 
  greater 
  than 
  the 
  

   individuals 
  figured. 
  

  

  Not 
  common. 
  

  

  Chonetes 
  undulata 
  n. 
  sp. 
  

  

  Plate 
  22, 
  Fig 
  15. 
  

  

  Chonetes 
  minima 
  Hall. 
  Doc. 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Explanation 
  

   of 
  pi. 
  22, 
  fig. 
  15. 
  1876. 
  Not 
  Chonetes 
  minima 
  Sowekby. 
  1839. 
  

  

  Shell 
  semicircular, 
  length 
  equal 
  to 
  six-tenths 
  of 
  the 
  width, 
  

   cardinal 
  line 
  straight, 
  greater 
  than 
  the 
  width 
  of 
  the 
  shell 
  

  

  