﻿Report 
  of 
  the 
  State 
  Geologist. 
  1055 
  

  

  oval 
  as 
  in 
  many 
  species 
  of 
  Dieiasma 
  ; 
  the 
  inverted 
  pedicle-sheath 
  

   or 
  collar 
  is 
  slightly 
  developed 
  within 
  the 
  aperture. 
  The 
  teeth 
  

   are 
  strong 
  and 
  supported 
  by 
  dental 
  lamellae 
  which 
  divide 
  the 
  

   umbonal 
  cavity 
  into 
  three 
  chambers 
  ; 
  near 
  the 
  apex 
  they 
  join 
  the 
  

   somewhat 
  thickened 
  scar 
  of 
  the 
  pedicle-muscle, 
  and 
  extend 
  

   beyond 
  its 
  anterior 
  margin 
  with 
  a 
  slight 
  convergence, 
  always 
  

   resting 
  on 
  the 
  bottom 
  of 
  the 
  valve. 
  The 
  pedicle-muscle 
  makes 
  

   the 
  strongest 
  scar 
  of 
  all 
  the 
  muscular 
  bands, 
  the 
  adductors 
  being 
  

   narrow 
  and 
  central, 
  and 
  the 
  diductors 
  scarcely 
  delimited. 
  

  

  In 
  the 
  brachial 
  valve 
  the 
  hinge-plate 
  is 
  large, 
  elongate 
  and 
  

   concave 
  ; 
  it 
  is 
  divided 
  by 
  two 
  low 
  ridges 
  diverging 
  from 
  the 
  

   apex, 
  and 
  from 
  these 
  the 
  plate 
  rises 
  toward 
  the 
  

   sides 
  into 
  decidedly 
  elevated 
  socket-walls 
  ; 
  between 
  

   the 
  diverging 
  ridges 
  the 
  surface 
  is 
  rather 
  deeply 
  

   depressed, 
  and, 
  toward 
  the 
  apex, 
  is 
  perforated 
  by 
  

   a 
  circular 
  foramen. 
  The 
  crura 
  are 
  slender, 
  very 
  

   short, 
  curving 
  inward 
  and 
  upward, 
  making 
  two 
  

   long 
  and 
  narrow 
  crural 
  apophyses. 
  The 
  descend- 
  

   ing 
  lamellae 
  are 
  carried 
  forward, 
  following 
  the 
  

   curves 
  of 
  the 
  valves 
  for 
  nearly 
  two-thirds 
  the 
  FlQ 
  " 
  495 
  . 
  C 
  ryp- 
  

   length 
  of 
  the 
  shell, 
  and 
  abruptly 
  reflected 
  ; 
  the 
  as- 
  %S? 
  %n, 
  lan 
  %Z 
  

   cending 
  lamellae 
  returning 
  to 
  within 
  a 
  short 
  dis- 
  i 
  n 
  r 
  | 
  e 
  the 
  U 
  ion| 
  °de- 
  

   tance 
  of 
  the 
  crural 
  apophyses. 
  The 
  whole 
  struc- 
  cending 
  g 
  iameiia} 
  as 
  

   ture 
  is 
  very 
  similar 
  to 
  the 
  brachidium 
  of 
  the 
  adult 
  living 
  MAGEL- 
  

   LAN^ 
  (WALDHEIMIA). 
  

  

  The 
  adductor 
  scars 
  are 
  more 
  or 
  less 
  distinct, 
  the 
  anterior 
  mem- 
  

   bers 
  being 
  the 
  more 
  clearly 
  denned. 
  These 
  scars 
  are 
  usually 
  

   represented 
  only 
  by 
  three 
  straight 
  lines 
  diverging 
  from 
  the 
  

   umbonal 
  region. 
  Vascular 
  sinuses 
  originate 
  about 
  the 
  muscular 
  

   areas 
  of 
  both 
  valves 
  and 
  are 
  directed 
  forward 
  with 
  frequent 
  

   ramifications. 
  

  

  The 
  shell-structure 
  is 
  highly 
  punctate. 
  

  

  Type. 
  Cryptonella 
  rectirostra, 
  Hall. 
  

  

  Distribution. 
  Devonian 
  — 
  Lower 
  Carboniferous. 
  

  

  Subgenus 
  Eunella, 
  Hall. 
  1893. 
  

   (Plate 
  52, 
  figs. 
  24-28.) 
  

   Shells 
  exteriorly 
  like 
  Cryptonella. 
  

  

  The 
  brachidium, 
  compared 
  with 
  that 
  of 
  Cbyptonella, 
  is 
  quite 
  

   short, 
  extending 
  less 
  than 
  one-half 
  the 
  length 
  of 
  the 
  brachial 
  

  

  113 
  

  

  