﻿Report 
  of 
  the. 
  State 
  Geologist. 
  1045 
  

  

  shell, 
  where 
  it 
  meets 
  a 
  similar 
  marginal 
  inflexion 
  from 
  the 
  oppo- 
  

   site 
  valve. 
  These 
  produce 
  the 
  sharp 
  introversion 
  of 
  the 
  lateral 
  

   margins 
  which 
  is 
  also 
  one 
  of 
  the 
  characteristics 
  of 
  the 
  genus 
  

   Megalanteris. 
  

  

  The 
  surface 
  of 
  the 
  valves 
  is 
  covered 
  with 
  fine, 
  hair-like 
  radiat- 
  

   ing 
  striae, 
  which 
  are 
  often 
  visible 
  only 
  near 
  the 
  margins 
  or 
  at 
  

   their 
  thickened 
  extremities 
  on 
  the 
  inflexed 
  portions 
  of 
  the 
  

   shell. 
  

  

  On 
  the 
  interior 
  the 
  dental 
  lamellae 
  are 
  short 
  and 
  do 
  not 
  rest 
  

   upon 
  the 
  valve. 
  The 
  hinge-plate 
  is 
  supported 
  by 
  two 
  vertical 
  

   septa, 
  the 
  median 
  cleft 
  and 
  visceral 
  foramen 
  are 
  more 
  or 
  less 
  

   obscured 
  and 
  with 
  sometimes 
  a 
  bilobed 
  callus 
  in 
  its 
  place. 
  The 
  

   brachidium 
  has 
  long, 
  straight 
  jugal 
  processes 
  and 
  the 
  triangular 
  

   anterior 
  plate 
  in 
  numerous 
  specimens 
  shows 
  that 
  the 
  posterior 
  

   rod-like 
  process 
  from 
  the 
  median 
  ridge 
  of 
  that 
  plate 
  extends 
  

   upward 
  almost 
  to 
  the 
  crura, 
  but 
  terminates 
  abruptly 
  and 
  has 
  no 
  

   connection 
  whatever 
  with 
  the 
  latter. 
  

  

  (Type, 
  Beachia 
  Suessana, 
  Hall. 
  Oriskany 
  sandstone). 
  

  

  Newberria, 
  Hall. 
  1S91. 
  

  

  (Plate 
  51, 
  figs. 
  12-19.) 
  

  

  Shell 
  elongate-ovoid, 
  having 
  the 
  general 
  contour 
  and 
  external 
  

   aspect 
  of 
  Kesssel^eeia 
  and 
  Amphigenia, 
  but 
  without 
  the 
  strongly 
  

   radiate-striate 
  surface 
  prevailing 
  in 
  the 
  former 
  genus 
  and 
  less 
  

   strongly 
  developed 
  in 
  the 
  latter. 
  The 
  greatest 
  convexity 
  of 
  the 
  

   valves 
  is 
  in 
  the 
  umbonal 
  region, 
  or 
  above 
  the 
  middle 
  of 
  their 
  

   length, 
  and 
  in 
  some 
  forms 
  the 
  surface 
  is 
  distinctly 
  flattened 
  over 
  

   the 
  lateral 
  slopes, 
  leaving 
  the 
  median 
  portion 
  of 
  the 
  valves 
  very 
  

   prominent 
  and 
  sometimes 
  subarigular. 
  The 
  cardinal 
  and 
  lateral 
  

   margins 
  are 
  regular, 
  even 
  and 
  not 
  inflected. 
  

  

  The 
  pedicle-valve 
  has 
  the 
  rostrum 
  produced 
  and 
  incurved, 
  the 
  

   apex 
  slightly 
  truncated 
  by 
  the 
  subcircular 
  foramen; 
  deltidial 
  

   plates 
  small 
  and 
  obscure. 
  The 
  teeth 
  are 
  comparatively 
  small, 
  

   projecting 
  forward 
  and 
  gently 
  upward, 
  free 
  at 
  their 
  extremities 
  

   and 
  supported 
  by 
  narrow 
  dental 
  plates 
  which 
  join 
  the 
  bottom 
  of 
  

   the 
  valve 
  above 
  the 
  middle 
  of 
  its 
  length 
  and 
  are 
  continued 
  for- 
  

   ward 
  as 
  slender, 
  widely 
  divergent 
  ridges 
  upon 
  the 
  inner 
  surface, 
  

   gradually 
  merging 
  into 
  the 
  shell. 
  

  

  103 
  

  

  