﻿INVEBTEBEATES. 
  325 
  

  

  Greatest 
  width 
  of 
  the 
  specimen 
  in 
  hand, 
  4f 
  inches; 
  height 
  of 
  

   the 
  outer 
  whorl, 
  1£ 
  inches. 
  

  

  Position 
  and 
  locality 
  : 
  The 
  only 
  specimen 
  seen 
  was 
  obtained 
  at 
  

   Montezuma, 
  Pike 
  county, 
  Illinois, 
  from 
  near 
  the 
  base 
  of 
  the 
  Bur- 
  

   lington 
  limestone. 
  

  

  No. 
  2,487, 
  of 
  the 
  Illinois 
  State 
  collection. 
  

  

  Dentalium 
  Illinoiensis, 
  Sp. 
  nov. 
  

  

  Shell 
  above 
  the 
  medium 
  size, 
  long, 
  straight 
  cylindrical, 
  slightly 
  

   tapering, 
  and 
  scarcely 
  inflated 
  at 
  the 
  aperture. 
  Surface 
  originally 
  

   smooth, 
  but 
  slightly 
  roughened 
  from 
  weathering 
  in 
  the 
  specimen 
  

   under 
  examination. 
  

  

  Length, 
  5| 
  inches; 
  width 
  near 
  the 
  aperture, 
  7-16 
  in. 
  

  

  This 
  species 
  differs 
  from 
  D. 
  Missouriense 
  of 
  Swallow, 
  in 
  its 
  larger 
  

   size, 
  smooth 
  surface 
  and 
  straight 
  form. 
  

  

  Position 
  and 
  locality 
  : 
  Lowest 
  beds 
  of 
  the 
  Chester 
  limestone, 
  Ches- 
  

   ter, 
  Illinois. 
  

  

  No, 
  2,488, 
  of 
  the 
  Illinois 
  State 
  collection. 
  

  

  Conulaeia 
  Chesterensis, 
  Sp. 
  nov. 
  

  

  Shell 
  attaining 
  a 
  medium 
  size, 
  long 
  and 
  rather 
  slender, 
  gradually 
  

   tapering, 
  nearly 
  equally 
  four 
  sided, 
  the 
  four 
  angles 
  being 
  distinctly 
  

   and 
  rather 
  deeply 
  furrowed, 
  while 
  a 
  slight 
  furrow 
  marks 
  the 
  median 
  

   line 
  on 
  each 
  side. 
  The 
  sides 
  are 
  crossed 
  by 
  numerous 
  raised 
  costae, 
  

   which 
  arch 
  slightly 
  forward 
  from 
  the 
  angles 
  to 
  the 
  median 
  line, 
  

   making 
  an 
  angle 
  with 
  that 
  line 
  of 
  about 
  14°. 
  They 
  do 
  not 
  cross 
  

   the 
  angular 
  furrows, 
  but 
  are 
  alternately 
  arranged 
  so 
  that 
  those 
  on 
  

   one 
  side 
  terminate 
  at 
  the 
  intervening 
  space 
  between 
  those 
  on 
  the 
  

   opposite 
  side. 
  These 
  spaces 
  are 
  about 
  twice 
  as 
  wide 
  as 
  the 
  cost*, 
  

   and 
  are 
  widest 
  at 
  the 
  median 
  line. 
  

  

  The 
  aperture 
  is 
  not 
  well 
  preserved 
  in 
  any 
  of 
  our 
  specimens, 
  but 
  

   the 
  shell 
  was 
  notched 
  at 
  the 
  angles 
  and 
  probably 
  contracted 
  at 
  the 
  

   aperture. 
  

  

  Length 
  of 
  a 
  rather 
  large 
  individual, 
  o 
  inches 
  ; 
  breadth 
  between 
  

   the 
  angles 
  near 
  the 
  aperture, 
  1 
  inch 
  ; 
  number 
  of 
  cost* 
  in 
  the 
  space 
  

   of 
  an 
  inch 
  near 
  the 
  aperture, 
  20; 
  near 
  the 
  apes, 
  80. 
  

  

  Position 
  and 
  locality 
  : 
  Chester 
  limestone, 
  Chester, 
  Illinois. 
  

  

  No. 
  2,489, 
  of 
  the 
  Illinois 
  State 
  collection. 
  

  

  