﻿992 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum, 
  

  

  ward 
  with 
  a 
  somewhat 
  less 
  curvature 
  than 
  the 
  plate 
  and 
  rises 
  to 
  

   the 
  highest 
  point 
  attained 
  by 
  the 
  latter 
  ; 
  the 
  inner 
  surface 
  of 
  this 
  

   process 
  is 
  deeply 
  grooved 
  and 
  at 
  its 
  base 
  it 
  is 
  supported 
  by 
  a 
  

  

  median 
  septum 
  which 
  extends 
  

   for 
  one-third 
  the 
  length 
  of 
  the 
  

   valve. 
  There 
  is 
  no 
  tent-shaped 
  

   structure 
  for 
  the 
  ^support 
  of 
  the 
  

   crura 
  as 
  in 
  Eumetria. 
  

  

  The 
  spirals 
  have 
  the 
  same 
  

   structure 
  as 
  in 
  Eumetria, 
  and 
  the 
  

   fig. 
  369.- 
  jugum 
  of 
  Hustedia 
  Mormoni, 
  posterior 
  margins 
  of 
  the 
  coils 
  are 
  

  

  Marcou 
  (sp.) 
  . 
  l 
  ° 
  . 
  

  

  fimbriated. 
  The 
  jugum, 
  also, 
  is 
  

   quite 
  similar 
  to 
  that 
  of 
  Eumetria 
  Verneuiliana, 
  terminating 
  in 
  

   a 
  long, 
  sharp, 
  retrally 
  directed 
  stem, 
  the 
  posterior 
  edges 
  of 
  the 
  

   lamellae 
  both 
  of 
  the 
  stem 
  and 
  the 
  lateral 
  branches 
  being 
  furnished 
  

   with 
  divergent 
  spinules. 
  The 
  extremity 
  of 
  the 
  stem 
  appears 
  to 
  

   be 
  simple. 
  

  

  Shell 
  strongly 
  punctate. 
  

  

  Type, 
  Hustedia 
  Mormoni, 
  Marcou 
  (sp.). 
  

  

  Distribution. 
  Coal 
  measures. 
  

  

  Trematospira, 
  Hall. 
  1859. 
  

   (Plate 
  38, 
  figs. 
  1-12.) 
  

  

  Shells 
  transverse, 
  subequally 
  convex, 
  with 
  median 
  fold 
  and 
  

   sinus 
  on 
  brachial 
  and 
  pedicle- 
  valves 
  respectively. 
  Surface 
  covered 
  

   with 
  radial, 
  coarse 
  or 
  fine, 
  simple 
  or 
  duplicate 
  plications. 
  Hinge- 
  

   line 
  straight, 
  often 
  long 
  ; 
  cardinal 
  extremities 
  abruptly 
  rounded 
  ; 
  

   anterior 
  margin 
  sinuate. 
  Umbo 
  of 
  the 
  pedicle-valve 
  incurved, 
  

   its 
  apex 
  truncated 
  by 
  a 
  circular 
  foramen. 
  Beneath 
  it 
  lies 
  the 
  

   deUhyrium, 
  which 
  is 
  covered 
  by 
  two 
  short 
  incurved 
  plates, 
  more 
  

   or 
  less 
  closely 
  anchylosed 
  along 
  the 
  median 
  suture, 
  and 
  so 
  greatly 
  

   thickened 
  on 
  their 
  interior 
  surface 
  as 
  to 
  appear 
  continuous 
  with 
  

   the 
  substance 
  of 
  the 
  valve. 
  

  

  The 
  deltarium 
  does 
  not 
  extend 
  downward 
  much 
  more 
  than 
  one 
  

   half 
  the 
  distance 
  from 
  the 
  apex 
  to 
  the 
  cardinal 
  margin, 
  leaving 
  

   beneath 
  it 
  a 
  crescentic 
  opening 
  which 
  is 
  occupied 
  by 
  the 
  beak 
  of 
  

   the 
  opposite 
  valve. 
  On 
  either 
  side 
  of 
  the 
  deltarium 
  is 
  a 
  narrow 
  

  

  5<> 
  

  

  