﻿1060 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  Hemiptychina, 
  Waagen. 
  1882. 
  

   Plicated 
  biconvex 
  shells 
  without 
  dental 
  plates, 
  but 
  with 
  the 
  

   hinge-structure 
  and 
  brachidiuni 
  of 
  Dielasma. 
  

  

  Fig. 
  505. 
  Hemiptychina 
  Himalayensis, 
  Davidson. 
  

  

  A 
  portion 
  of 
  the 
  interior; 
  showing 
  the 
  absence 
  of 
  dental 
  plates 
  in 
  the 
  pedicle-valve, 
  and 
  the 
  

   DiELASMA-like 
  brachidium. 
  (Waagen.) 
  

  

  Type, 
  Hemiptychina 
  Himalayensis, 
  Davidson 
  (sp.). 
  

   Distribution. 
  Carboniferous 
  — 
  Permian. 
  

  

  Beecheria, 
  Hall. 
  1893. 
  

   (Plate 
  53, 
  figs. 
  1-3.) 
  

   Non-plicated 
  shells 
  in 
  which 
  the 
  dental 
  plates 
  are 
  absent 
  or 
  

   represented 
  only 
  by 
  faint 
  ridges 
  which 
  do 
  not 
  reach 
  the 
  bottom 
  

   of 
  the 
  pedicle-valve. 
  

  

  The 
  peculiar 
  myiferous 
  hinge-plate 
  of 
  Dielasma 
  is 
  wholly 
  

   merged 
  with 
  the 
  valve, 
  but 
  the 
  crural 
  ridges 
  are 
  still 
  retained 
  and 
  

   the 
  descending 
  lamellae 
  originate 
  from 
  them 
  at 
  the 
  bottom 
  of 
  the 
  

  

  Fig. 
  506. 
  Beecheria 
  subloevis, 
  Waagen 
  (sp.) 
  

   Dorsal 
  view: 
  showing 
  the 
  smooth 
  exterior. 
  (Waagen.) 
  

   Fig 
  507. 
  Beecheria 
  Davidsoni, 
  Hall. 
  

   An 
  enlarged 
  profile 
  of 
  the 
  brachidium; 
  showing 
  the 
  manner 
  in 
  which 
  lamellae 
  arise 
  from 
  the 
  

  

  bottom 
  of 
  the 
  valve, 
  the 
  broad 
  posterior 
  jugal 
  processes 
  and 
  the 
  much 
  narrower 
  descend. 
  

  

  ing 
  lamellae. 
  The 
  anterior 
  transverse 
  or 
  reflected 
  band 
  is 
  not 
  fully 
  retained. 
  

  

  valve 
  in 
  very 
  much 
  the 
  same 
  way 
  as 
  in 
  Dielasma. 
  The 
  crural 
  

   apophyses 
  are 
  broad 
  and 
  erect, 
  there 
  being 
  no 
  part 
  of 
  the 
  descend- 
  

   ing 
  branches 
  behind 
  them. 
  Sometimes 
  the 
  brachial 
  valve 
  retains 
  

   a^low 
  muscular 
  impression 
  which 
  has 
  the 
  form 
  of 
  the 
  platform 
  of 
  

   Dielasma. 
  

  

  Type, 
  Beecheria 
  Davidsoni, 
  Hall. 
  * 
  

  

  Distribution. 
  Carboniferous. 
  

  

  118 
  

  

  