﻿Report 
  of 
  the 
  State 
  Geologist. 
  963 
  

  

  Hindella, 
  Davidson. 
  1882. 
  

   (Plate 
  32, 
  figs. 
  18-20.) 
  

  

  Shells 
  subcircular 
  or 
  elongate-ovate 
  in 
  outline 
  ; 
  valves 
  convex, 
  

   the 
  pedicle-valve 
  being 
  gibbous 
  in 
  the 
  umbonal 
  region. 
  The 
  

   hinge-line 
  is 
  very 
  short 
  but 
  the 
  cardinal 
  slopes 
  are 
  frequently 
  

   long 
  and 
  transverse, 
  which, 
  with 
  the 
  fulness 
  of 
  the 
  beaks 
  of 
  both 
  

   valves, 
  produce 
  a 
  " 
  shouldered 
  " 
  appearance. 
  There 
  is 
  a 
  low 
  sinus 
  

   on 
  the 
  pedicle-valve 
  which 
  is 
  apparent 
  only 
  over 
  the 
  pallial 
  

   region; 
  this 
  is 
  accompanied 
  by 
  a 
  slight 
  fold 
  on 
  the 
  opposite 
  

   valve. 
  

  

  The 
  apex 
  of 
  the 
  pedicle-valve 
  is 
  closely 
  incurved, 
  concealing 
  

   both 
  deltidial 
  plates 
  and 
  foramen. 
  On 
  the 
  interior 
  the 
  teeth 
  are 
  

   moderately 
  prominent 
  and 
  are 
  supported 
  by 
  strong 
  dental 
  plates, 
  

  

  Figs. 
  305, 
  306. 
  The 
  primary 
  lamell© 
  and 
  jugum 
  of 
  Hindella 
  umbonata, 
  Billings 
  (sp.). 
  

  

  which 
  not 
  only 
  extend 
  to 
  the 
  bottom 
  of 
  the 
  valve, 
  but 
  are 
  con- 
  

   tinued 
  forward 
  for 
  about 
  one-third 
  the 
  length 
  of 
  the 
  shell, 
  and 
  

   inclose 
  a 
  narrow, 
  elongate 
  muscular 
  area. 
  In 
  the 
  brachial 
  valve 
  

   the 
  hinge-plate 
  appears 
  to 
  be 
  short 
  and 
  constructed 
  on 
  the 
  same 
  

   plan 
  as 
  that 
  of 
  Meristina 
  and 
  Whitfieldell.a, 
  with 
  two 
  diverg- 
  

   ing 
  crural 
  bases 
  divided 
  by 
  a 
  median 
  groove, 
  or 
  a 
  subtriangular 
  

   pit, 
  and 
  is 
  supported 
  by 
  a 
  median 
  septum 
  extending 
  for 
  about 
  

   one-half 
  the 
  length 
  of 
  the 
  valve. 
  Spirals 
  everted 
  ; 
  jugum 
  situated 
  

   anteriorly, 
  very 
  depressed, 
  the 
  lateral 
  processes 
  being 
  directed 
  

   backward 
  in 
  a 
  low 
  upward 
  curve, 
  uniting 
  to 
  form 
  a 
  short, 
  straight 
  

   undivided 
  stem. 
  External 
  surface 
  smooth. 
  Shell-structure 
  

   fibrous, 
  impunctate. 
  

  

  Type, 
  Hindella 
  umbonata, 
  Billings 
  (sp.). 
  

  

  Two 
  species 
  are 
  known, 
  both 
  from 
  the 
  Middle 
  Silurian. 
  

  

  21 
  

  

  