﻿INVERTEBEATES. 
  

  

  319 
  

  

  LAM 
  ELL 
  I 
  BRANCH 
  I 
  AT 
  A 
  

  

  Genus 
  CHJENOMYA, 
  Meek. 
  

  

  CELENOMYA 
  MAEIA, 
  Worthen. 
  

  

  a 
  Side 
  view. 
  6 
  Dorsal 
  view, 
  nat. 
  size. 
  

   Choenomya 
  Maria, 
  Worthen, 
  February, 
  1882. 
  

   Bulletin 
  No. 
  1. 
  of 
  the 
  Illinois 
  State 
  Museum 
  of 
  Natural 
  History, 
  p. 
  39. 
  

  

  Shell 
  elongate, 
  sub-cylin- 
  

   drical, 
  anterior 
  side 
  much 
  

   compressed 
  and 
  aperture 
  en- 
  

   tirely 
  closed; 
  posterior 
  side 
  

   truncated 
  and 
  widely 
  gaping. 
  

   Base 
  slightly 
  convex 
  in 
  out- 
  

   line, 
  rounding 
  up 
  gradually 
  

   in 
  front 
  and 
  abruptly 
  be- 
  

   hind, 
  dorsal 
  side 
  a 
  little 
  

   concave 
  from 
  the 
  beaks 
  

   01 
  to 
  the 
  posterior 
  extremity. 
  

   Beaks 
  depressed, 
  incurved, 
  

   and 
  located 
  about 
  one- 
  

   fifth 
  the 
  entire 
  length 
  of 
  the 
  shell 
  from 
  the 
  anterior 
  side. 
  

  

  Two 
  conspicuous 
  furrows 
  commence 
  at 
  the 
  beak, 
  the 
  anterior 
  one 
  

   crossing 
  the 
  valve 
  obliquely 
  to 
  the 
  base 
  of 
  the 
  shell 
  at 
  a 
  point 
  about 
  

   two-fifths 
  of 
  its 
  entire 
  length 
  from 
  the 
  anterior 
  side; 
  the 
  posterior 
  

   one 
  crossing 
  the 
  shell 
  much 
  more 
  obliquely, 
  and 
  terminating 
  at 
  the 
  

   base 
  of 
  the 
  shell, 
  near 
  its 
  posterior 
  extremity. 
  

  

  