﻿Report 
  of 
  the 
  State 
  Geologist. 
  365 
  

  

  Of 
  two 
  specimens 
  of 
  this 
  Orthoceras 
  one 
  has 
  12 
  annulations 
  in 
  

   a 
  length 
  of 
  28 
  mm., 
  the 
  other 
  has 
  the 
  same 
  number 
  in 
  a 
  length 
  

   of 
  40 
  mm. 
  

  

  Both 
  are 
  from 
  the 
  limestone 
  layer 
  in 
  the 
  Marcellus 
  shales 
  at 
  

   854 
  feet 
  in 
  the 
  Shaft. 
  

  

  Orthoceras 
  CEdipus, 
  Rail. 
  

  

  Plate 
  II, 
  fig. 
  12. 
  

  

  Palaeontology 
  of 
  New 
  York, 
  vol. 
  v, 
  pt. 
  2, 
  p. 
  294, 
  pi. 
  37, 
  fig. 
  6. 
  

  

  pi. 
  82, 
  fig. 
  17. 
  

  

  This 
  species, 
  which 
  is 
  very 
  abundant 
  in 
  the 
  Hamilton 
  shales 
  from 
  

   473 
  to 
  488 
  feet 
  in 
  the 
  Shaft, 
  was 
  described 
  from 
  specimens 
  whose 
  

   exterior 
  was 
  very 
  imperfectly 
  preserved. 
  An 
  enlargement 
  of 
  

   the 
  outer 
  ornamentation 
  is 
  therefore 
  given 
  here 
  from 
  a 
  very 
  per- 
  

   fectly 
  preserved 
  example. 
  The 
  sculpture 
  consists 
  of 
  a 
  series 
  of 
  

   longitudinal 
  ridges 
  of 
  variable 
  size, 
  those 
  of 
  the 
  first 
  order 
  being 
  

   only 
  approximately 
  equidistant 
  and 
  the 
  intervals 
  filled 
  by 
  ridges 
  

   of 
  two 
  or 
  three 
  lesser 
  sizes, 
  at 
  unequal 
  intervals. 
  All 
  are 
  crossed 
  

   by 
  very 
  sharp, 
  closely- 
  set 
  concentric 
  stride, 
  which 
  make 
  a 
  slight 
  

   node 
  at 
  their 
  junction. 
  

  

  (jomphoceras 
  mitriformis, 
  sp. 
  no 
  v. 
  

   Plate 
  III, 
  fig. 
  1. 
  

   The 
  specimens 
  upon 
  which 
  this 
  species 
  is 
  based 
  is 
  an 
  individual 
  

   which 
  lacks 
  the 
  apex 
  only, 
  but 
  has 
  been 
  compressed 
  in 
  the 
  shales, 
  

   without 
  distortion 
  of 
  outline. 
  It 
  is 
  a 
  quite 
  symmetrical 
  shell, 
  

   widening 
  from 
  a 
  moderately 
  broad 
  aperture 
  and 
  attaining 
  its 
  

   greatest 
  diameter 
  at 
  a 
  point 
  just 
  posterior 
  to 
  the 
  middle 
  of 
  its 
  

   length, 
  whence 
  it 
  tapers 
  rapidly, 
  with 
  a 
  convex 
  curve 
  for 
  a 
  por- 
  

   tion 
  of 
  the 
  distance, 
  and 
  concave 
  margins 
  posteriorly, 
  to 
  a 
  very 
  

   narrow 
  if 
  not 
  acute 
  inception. 
  • 
  The 
  entire 
  length 
  of 
  the 
  specimen 
  

   is 
  135 
  mm. 
  ; 
  its 
  width 
  at 
  the 
  aperture, 
  40 
  mm. 
  ; 
  its 
  width 
  at 
  a 
  

   distance 
  of 
  60 
  mm. 
  from 
  the 
  aperture, 
  51 
  mm. 
  The 
  external 
  sur- 
  

   face 
  is 
  smooth 
  and 
  so 
  preserved 
  as 
  to 
  show 
  but 
  little 
  evidence 
  of 
  

   septa, 
  the 
  first 
  of 
  these 
  being 
  at 
  a 
  distance 
  of 
  39 
  mm. 
  from 
  the 
  

   aperture. 
  The 
  apical 
  portion 
  of 
  the 
  shell 
  retains 
  traces 
  of 
  the 
  

   siphuncular 
  beads, 
  13 
  of 
  these 
  being 
  exhibited 
  in 
  a 
  distance 
  of 
  

   18 
  mm., 
  showing 
  the 
  very 
  close 
  approximation 
  of 
  the 
  septa 
  in 
  

   this 
  part 
  of 
  the 
  shell. 
  

  

  