﻿Fig. 
  

  

  4. 
  

  

  Fig. 
  

  

  5. 
  

  

  Fig. 
  

  

  6. 
  

  

  Fig. 
  

  

  7. 
  

  

  Fig. 
  

  

  8. 
  

  

  PLATE 
  XXII. 
  

  

  Steophonella 
  semifasciata 
  Hall. 
  

  

  Page 
  154. 
  

  

  Fig. 
  1. 
  An 
  imperfect 
  dorsal 
  valve. 
  

  

  Fig. 
  2. 
  A 
  more 
  nearly 
  entire 
  specimen 
  of 
  the 
  same 
  valve, 
  "which 
  presents 
  the 
  

   usual 
  fasciculate 
  characters 
  of 
  surface-striae. 
  

  

  Fig. 
  3. 
  Cardinal 
  view 
  of 
  a 
  specimen, 
  retaining 
  both 
  valves 
  in 
  place 
  and 
  show- 
  

   ing 
  strong 
  deltidial 
  coverings. 
  

  

  Strophomexa 
  rhomboid 
  alis 
  ( 
  Wilchens). 
  

   Page 
  150. 
  

   The 
  interior 
  of 
  a 
  ventral 
  valve, 
  showing 
  the 
  muscular 
  imprint. 
  

   The 
  dorsal 
  view 
  of 
  a 
  specimen, 
  having 
  both 
  valves 
  in 
  connection. 
  

   The 
  ventral 
  valve 
  of 
  the 
  same. 
  

   A 
  lateral 
  view 
  of 
  another 
  specimen, 
  with 
  a 
  ventral 
  valve 
  of 
  Crania 
  

  

  Siluriana 
  attached. 
  

   The 
  upper 
  part 
  of 
  a 
  ventral 
  valve 
  of 
  a 
  large 
  specimen, 
  which 
  preserves 
  

   both 
  valves, 
  the 
  cardinal 
  line 
  being 
  shown 
  near 
  the 
  lateral 
  angles. 
  

   Fig. 
  9. 
  The 
  interior 
  of 
  a 
  dorsal 
  valve, 
  showing 
  muscular 
  imprints, 
  cardinal 
  

  

  process, 
  etc. 
  

   Fig. 
  10. 
  An 
  enlargement 
  of 
  the 
  middle 
  portion 
  of 
  the 
  cardinal 
  area 
  of 
  a 
  speci- 
  

   men, 
  with 
  both 
  valves 
  in 
  place, 
  showing 
  the 
  back 
  of 
  the 
  cardinal 
  

   process 
  of 
  the 
  dorsal 
  valve 
  filling 
  the 
  deltidial 
  opening 
  of 
  the 
  ven- 
  

   tral 
  valve. 
  The 
  central 
  groove 
  marks 
  the 
  division 
  of 
  the 
  cardinal 
  

   process. 
  

  

  Choxetes 
  ^ova-Scotica 
  Hall. 
  

   Pasre 
  155. 
  

  

  Fig. 
  11. 
  A 
  ventral 
  valve 
  showing 
  the 
  spines 
  and 
  the 
  larger 
  median 
  strise 
  ; 
  

  

  enlarged 
  to 
  two 
  diameters. 
  

   Figs. 
  12, 
  13. 
  Two 
  other 
  ventral 
  valves, 
  natural 
  size, 
  showing 
  the 
  cardinal 
  spines. 
  

  

  The 
  central 
  part 
  of 
  these 
  three 
  figures 
  is 
  incorrectly 
  represented 
  as 
  

  

  angular, 
  instead 
  of 
  simply 
  by 
  a 
  stronger 
  median 
  ray. 
  

   Fig. 
  14. 
  An 
  enlargement 
  from 
  the 
  middle 
  of 
  a 
  specimen 
  to 
  show 
  the 
  stronger 
  

  

  central 
  ray 
  and 
  fine 
  concentric 
  strias. 
  

  

  Choxetes 
  uxdulata 
  n. 
  sp. 
  

  

  Page 
  155. 
  

  

  Fig. 
  15. 
  An 
  enlargement 
  to 
  four 
  diameters 
  of 
  an 
  individual 
  possessing 
  the 
  usual 
  

   characters. 
  

  

  