﻿Report 
  of 
  the 
  State 
  Geologist, 
  

  

  1005 
  

  

  Glassia, 
  Davidson. 
  1881. 
  

   (Plate 
  40, 
  figs. 
  9-12.) 
  

  

  Shells 
  small, 
  biconvex 
  ; 
  elongate-ovate 
  in 
  outline 
  ; 
  surface 
  

   smooth. 
  Umbo 
  of 
  the 
  pedicle-valve 
  not 
  

   conspicuous; 
  beak 
  depressed. 
  Structure 
  

   of 
  the 
  deltidium 
  and 
  hinge 
  as 
  in 
  Nucle- 
  

   ospira. 
  Muscular 
  impression 
  consisting 
  

   of 
  two 
  widely 
  divergent, 
  oval 
  diductor 
  

   scars, 
  between 
  which 
  lies 
  a 
  broad 
  

   adductor 
  scar. 
  

  

  Brachial 
  valve 
  with 
  an 
  internal 
  sep- 
  

   tum. 
  The 
  spiral 
  cones 
  have 
  their 
  bases 
  Fig 
  m 
  Glassiaobovata 
  , 
  Sow 
  . 
  

   toward 
  the 
  lateral 
  margins 
  of 
  the 
  shell 
  erby(sp.) 
  in 
  eriorof 
  tnepedicie- 
  

   and 
  their 
  apices 
  at 
  the 
  center 
  of 
  the 
  

  

  internal 
  cavity 
  ; 
  their 
  position 
  with 
  reference 
  to 
  each 
  other 
  

   is, 
  therefore, 
  just 
  the 
  reverse 
  of 
  that 
  in 
  Meristella, 
  Retzia, 
  

   etc. 
  The 
  cones 
  are 
  laterally 
  compressed, 
  and 
  the 
  ribbon 
  

   makes 
  but 
  few 
  volutions. 
  The 
  jugum 
  originates 
  as 
  in 
  Atrypa, 
  

  

  Fig. 
  

  

  Braehidium 
  of 
  Glassia 
  obovata, 
  Sowerby 
  (sp.). 
  (Davidson.) 
  

  

  is 
  continuous, 
  bending 
  downward 
  into 
  the 
  space 
  between 
  the 
  

   cones 
  and 
  making 
  a 
  sharp 
  angle 
  at 
  the 
  point 
  of 
  union, 
  which 
  

   may 
  be 
  directed 
  upward. 
  

  

  Type, 
  Glassia 
  obovata, 
  Sowerby 
  (sp.). 
  

  

  Distribution. 
  Lower 
  Silurian 
  — 
  Middle 
  Devonian. 
  

  

  03 
  

  

  