﻿848 
  JBorttseventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  Parastrophia 
  divergens, 
  sp. 
  nov. 
  

   (Plate 
  lxiii, 
  figs. 
  4-7.) 
  

  

  Shells 
  of 
  medium 
  size 
  with 
  strongly 
  convex 
  brachial 
  valve 
  and 
  

   depressed 
  convex, 
  anteriorly 
  concave 
  pedicle- 
  valve. 
  The 
  beak 
  of 
  

   the 
  pedicle- 
  valve 
  is 
  erect, 
  but 
  not 
  conspicuous 
  ; 
  from 
  the 
  gently 
  

   convex 
  umbo 
  the 
  surface 
  slopes 
  gradually 
  to 
  the 
  lateral 
  margins, 
  

   and 
  abruptly 
  to 
  the 
  front, 
  forming 
  a 
  broad 
  and 
  deep 
  sinus, 
  which 
  

   is 
  sharply 
  defined 
  at 
  the 
  sides, 
  and 
  bears 
  from 
  two 
  to 
  four 
  angu- 
  

   lar 
  plications. 
  Two 
  or 
  more 
  smaller 
  plications 
  occur 
  on 
  each 
  

   lateral 
  slope. 
  

  

  The 
  brachial 
  valve 
  is 
  well 
  rounded 
  in 
  the 
  umbonal 
  region, 
  but 
  

   the 
  median 
  fold 
  is 
  defined 
  only 
  near 
  the 
  anterior 
  margin. 
  It 
  

   bears 
  from 
  three 
  to 
  five 
  plications, 
  with 
  three 
  on 
  each 
  lateral 
  

   slope. 
  All 
  the 
  plications, 
  as 
  well 
  as 
  fold 
  and 
  sinus, 
  become 
  obso- 
  

   lete 
  in 
  the 
  umbonal 
  region, 
  and 
  in 
  old 
  and 
  thickened 
  shells 
  the 
  

   latter 
  can 
  be 
  distinguished 
  only 
  at 
  the 
  anterior 
  margins 
  of 
  the 
  

   valves. 
  

  

  In 
  the 
  interior 
  there 
  is 
  a 
  supported 
  spondylium 
  in 
  the 
  pedicle- 
  

   valve, 
  but 
  in 
  the 
  brachial 
  valve 
  the 
  septal 
  plates 
  do 
  not 
  unite. 
  

  

  Hudson 
  Kiver 
  group. 
  Wilmington, 
  Illinois. 
  

  

  Parastrophia 
  Greenii, 
  sp. 
  nov. 
  

   (Plate 
  lxiii, 
  figs. 
  17-20, 
  22.) 
  

  

  Shell 
  robust, 
  with 
  convex 
  brachial 
  valve 
  and 
  shallow 
  pedicle- 
  

   valve 
  convex 
  in 
  the 
  umbonal 
  region 
  but 
  concave 
  anteriorly. 
  

   Beaks 
  not 
  prominent; 
  that 
  of 
  the 
  pedicle-valve 
  low 
  bat 
  erect, 
  that 
  

   of 
  the 
  brachial 
  valve 
  full 
  and 
  incurved. 
  Cardinal 
  slopes 
  sharply 
  

   defined 
  on 
  pedicle-valve. 
  Median 
  fold 
  and 
  sinus 
  on 
  brachial 
  and 
  

   pedicle-valves 
  not 
  strongly 
  defined 
  except 
  at 
  the 
  anterior 
  margin. 
  

   The 
  brachial 
  valve 
  bears 
  six 
  broadly 
  rounded 
  plications 
  which 
  

   are 
  obsolete 
  in 
  the 
  umbonal 
  region 
  ; 
  four 
  of 
  these 
  belong 
  to 
  the 
  

   median 
  fold, 
  the 
  other 
  two 
  to 
  the 
  lateral 
  slopes. 
  The 
  pedicle- 
  

   valve 
  has 
  fiYQ 
  plications, 
  with 
  three 
  in 
  the 
  median 
  sinus. 
  Interior 
  

   with 
  a 
  median 
  supporting 
  septum 
  in 
  each 
  valve. 
  

  

  Niagara 
  dolomites. 
  Wear 
  Milwaukee, 
  Wisconsin. 
  

  

  Parastrophia 
  multiplicata, 
  sp. 
  nov. 
  

  

  (Plate 
  lxiii, 
  figs. 
  15, 
  16, 
  21.) 
  

  

  This 
  species 
  differs 
  from 
  P. 
  Greenii 
  in 
  its 
  more 
  conspicuously 
  

  

  developed 
  median 
  fold 
  and 
  sinus, 
  flatter 
  and 
  larger 
  plications, 
  and 
  

  

  the 
  greater 
  number 
  of 
  the 
  latter 
  * 
  on 
  the 
  lateral 
  slopes. 
  The 
  

  

  