﻿Descriptions 
  of 
  New 
  Species 
  Figured 
  in 
  

   Volume 
  VIII, 
  Part 
  2. 
  

  

  Orthis 
  ? 
  glypta, 
  sp. 
  no 
  v. 
  

   (Plate 
  lxxxiv, 
  figs. 
  8, 
  9.) 
  

  

  Shell 
  small, 
  transverse, 
  with 
  long, 
  straight 
  hinge, 
  making 
  the 
  

   greatest 
  diameter 
  of 
  the 
  shell; 
  short 
  along 
  the 
  median 
  axis; 
  

   marginal 
  outline 
  transversely 
  subelliptical. 
  Pedicle-valve 
  with 
  a 
  

   broad 
  and 
  low 
  median 
  sinus 
  and 
  generally 
  depressed 
  surface. 
  

   The 
  exterior 
  bears 
  from 
  twelve 
  to 
  sixteen 
  low, 
  flat 
  plications, 
  

   separated 
  by 
  narrow 
  sulci, 
  and 
  sometimes 
  with 
  a 
  fine 
  groove 
  on 
  

   the 
  surface 
  of 
  each. 
  These 
  extend 
  from 
  apex 
  to 
  margins, 
  and 
  

   are 
  crossed 
  by 
  fine, 
  undulating, 
  subconcentric 
  lines 
  apparently 
  in 
  

   two 
  oblique 
  sets, 
  producing 
  a 
  peculiarly 
  reticulated 
  or 
  wavy 
  

   surface 
  similar 
  to 
  that 
  occurring 
  in 
  the 
  Swedish 
  Silurian 
  species, 
  

   0. 
  Zoveni, 
  Lindstrom. 
  The 
  muscular 
  area 
  of 
  the 
  pedicle- 
  valve 
  is 
  

   small. 
  Length 
  of 
  an 
  average 
  pedicle-valve, 
  12mm. 
  ; 
  width, 
  18 
  mm. 
  

  

  .Niagara 
  dolomites. 
  Near 
  Milwaukee, 
  Wisconsin. 
  

  

  Strophonella 
  costatula, 
  sp. 
  nov. 
  

   (Plate 
  lxxxiv, 
  figs. 
  15, 
  16.) 
  

  

  Shell 
  subsemicircular 
  in 
  outline; 
  hinge-line 
  straight 
  or 
  slightly 
  

   arched 
  ; 
  surface 
  depressed 
  concavo-convex. 
  

  

  Pedicle-valve 
  elevated 
  at 
  the 
  beak, 
  becoming 
  rapidly 
  depressed 
  

   anteriorly, 
  the 
  median 
  depression 
  continued 
  on 
  to 
  a 
  short 
  lingui 
  

   form 
  extension 
  at 
  the 
  anterior 
  margin. 
  Corresponding 
  to 
  this 
  

   depression 
  is 
  a 
  broad 
  anterior 
  fold 
  on 
  the 
  opposite 
  valve. 
  The 
  

   surface 
  of 
  both 
  valves 
  is 
  covered 
  with 
  a 
  few 
  coarse, 
  round, 
  sharply 
  

   elevated 
  ribs, 
  which 
  rapidly 
  bifuracate 
  or 
  multiply 
  by 
  implanta- 
  

   tion. 
  These 
  are 
  more 
  or 
  less 
  irregular 
  or 
  sinuous, 
  elevated 
  at 
  

   the 
  concentric 
  varices 
  and 
  crossed 
  by 
  faint 
  concentric 
  lines. 
  

  

  The 
  typical 
  example 
  has 
  a 
  length 
  of 
  21 
  mm. 
  and 
  a 
  width 
  on 
  

   the 
  hinge 
  of 
  24 
  mm. 
  

  

  Niagara 
  group. 
  Louisville, 
  Kentucky. 
  

   106 
  

  

  