﻿T. 
  DAVIDSON 
  AND 
  W. 
  KING 
  ON 
  THE 
  TRIMERELLID^. 
  171 
  

  

  Plate 
  XYI. 
  

  

  Fig. 
  1. 
  Trimerella 
  acuminata. 
  Interior 
  of 
  brachial 
  valve: 
  N, 
  cavity 
  under 
  

   platform 
  exposed. 
  

  

  2. 
  Interior 
  of 
  pedicle-valve 
  : 
  N, 
  cavity 
  under 
  platform 
  exposed 
  ; 
  O, 
  um- 
  

  

  bonal 
  chamber. 
  These 
  moulds 
  were 
  taken 
  from 
  the 
  internal 
  cast 
  figured 
  

   in 
  PI. 
  XV. 
  fig. 
  4 
  : 
  the 
  beak 
  is 
  added 
  in 
  fig. 
  2. 
  Guelph 
  limestone, 
  Hes- 
  

   pelar, 
  Ontario. 
  

  

  3. 
  T. 
  ohioensis, 
  Meek. 
  Internal 
  cast, 
  showing 
  the 
  pedicle-valve. 
  

  

  4. 
  . 
  The 
  same 
  cast, 
  showing 
  the 
  hinge-characters 
  of 
  both 
  valves. 
  

  

  Niagara 
  Group, 
  Upper 
  Silurian, 
  Otwa 
  Comity, 
  Ohio. 
  

  

  5. 
  . 
  Internal 
  cast 
  of 
  brachial 
  valve. 
  Same 
  locality. 
  

  

  6. 
  . 
  Gutta-percha 
  mould 
  taken 
  from 
  the 
  hinge 
  portion 
  of 
  the 
  

  

  cast 
  so 
  as 
  to 
  show 
  ridge-like 
  cardinal 
  process, 
  &c. 
  Specimens 
  3 
  to 
  5 
  

   were 
  sent 
  us 
  for 
  illustration 
  by 
  Mr. 
  Meek. 
  

  

  7. 
  . 
  Gutta-percha 
  mould 
  of 
  brachial 
  valve, 
  taken 
  from 
  an 
  internal 
  

  

  cast 
  in 
  the 
  possession 
  of 
  Mr. 
  Whitfield, 
  of 
  Albany. 
  This 
  mould 
  shows 
  

   the 
  cardinal 
  process 
  in 
  the 
  form 
  of 
  two 
  circular 
  depressions 
  in 
  the 
  centre 
  

   of 
  the 
  hinge, 
  also 
  indications 
  of 
  rude 
  articulation 
  (elongated 
  plates) 
  of 
  

   the 
  valves. 
  From 
  the 
  Niagara 
  Group 
  of 
  Yellow 
  Spring, 
  Ohio. 
  

  

  8. 
  Trimerella 
  Sillingsii, 
  Dall. 
  Internal 
  cast 
  of 
  pedicle-valve. 
  

  

  9. 
  . 
  Gutta-percha 
  mould 
  taken 
  from 
  the 
  same 
  cast 
  so 
  as 
  to 
  show 
  

  

  the 
  interior 
  of 
  the 
  valve. 
  Guelph 
  Limestone, 
  New 
  Hope, 
  West 
  Canada 
  : 
  

   Museum 
  of 
  Montreal. 
  

  

  Plate 
  XVII. 
  

  

  Figs. 
  1, 
  la, 
  b. 
  Monomerella 
  Walmstedti, 
  n. 
  sp. 
  A 
  perfect 
  testiferous 
  specimen. 
  

   " 
  Central 
  Gotland," 
  Klinteberg, 
  Gotland 
  : 
  Museum 
  of 
  Wisby 
  College. 
  

   Interior 
  of 
  pedicle-valve. 
  

  

  Interior 
  of 
  brachial 
  valve. 
  Same 
  museum 
  and 
  locality. 
  

   Internal 
  cast 
  of 
  pedicle-valve. 
  Same 
  formation 
  : 
  Island 
  

   Coll. 
  of 
  Herr 
  Fegrceus. 
  

  

  prisca, 
  Billings. 
  Internal 
  cast 
  of 
  both 
  valves 
  in 
  con- 
  

   Fig. 
  5. 
  The 
  pair 
  of 
  scars 
  (the 
  impression 
  on 
  middle) 
  

   belong 
  to 
  the 
  brachial 
  valve. 
  Guelph 
  Limestone, 
  Hespelar, 
  Ontario 
  : 
  

   Museum 
  of 
  Montreal. 
  

  

  6, 
  6 
  a. 
  . 
  6, 
  internal 
  cast 
  of 
  pedicle-valve. 
  6 
  a, 
  gutta-percha 
  

  

  mould 
  taken 
  from 
  the 
  same 
  cast, 
  showing 
  the 
  interior 
  of 
  the 
  valve. 
  

   Same 
  locality 
  and 
  museum. 
  

  

  7. 
  . 
  Interior 
  of 
  the 
  pedicle-valve, 
  taken 
  in 
  gutta-percha 
  from 
  a 
  

  

  large 
  internal 
  cast. 
  Same 
  locality. 
  

   8. 
  . 
  Interior 
  of 
  brachial 
  valve 
  of 
  same 
  species, 
  taken 
  in 
  gutta- 
  

   percha 
  from 
  an 
  internal 
  cast. 
  Same 
  locality. 
  

  

  9, 
  9 
  a, 
  b, 
  c. 
  Lindstroemi, 
  n. 
  sp. 
  9, 
  9 
  a, 
  internal 
  cast. 
  9 
  b, 
  showing 
  both 
  

  

  valves 
  in 
  conjunction. 
  9 
  c, 
  interior 
  of 
  pedicle-valve 
  from 
  a 
  gutta-percha 
  

   mould. 
  "Wisby 
  Strata," 
  near 
  Wisby, 
  Gotland. 
  

  

  10, 
  10 
  a. 
  orbicularis, 
  Bill. 
  10, 
  external 
  cast 
  of 
  brachial 
  valve 
  ; 
  10 
  a, 
  

  

  of 
  pedicle-valve. 
  Guelph 
  Limestone, 
  Elora, 
  Ontario 
  : 
  Museum 
  of 
  

   Montreal. 
  

  

  Plate 
  XVIII. 
  

  

  Fig. 
  1. 
  Dinobolus 
  Conradi, 
  Hall. 
  Interior 
  of 
  pedicle- 
  valve 
  from 
  a 
  gutta-percha 
  

   mould. 
  

  

  2. 
  . 
  Another 
  specimen. 
  Same 
  valve, 
  showing 
  deep 
  vault, 
  n, 
  ex- 
  

   tending 
  under 
  the 
  platform. 
  From 
  Niagara 
  limestone, 
  Leclaire, 
  Iowa. 
  

   Collection 
  of 
  Prof. 
  Hall. 
  

  

  3. 
  . 
  Interior 
  of 
  brachial 
  valve. 
  

  

  4. 
  . 
  Internal 
  cast 
  of 
  pedicle-valve. 
  

  

  5. 
  . 
  Natural 
  cast 
  of 
  brachial 
  valve. 
  Same 
  museum 
  and 
  locality. 
  

  

  6, 
  6 
  a. 
  Davidsoni, 
  Salter. 
  Exterior. 
  Wenlock 
  shale, 
  near 
  Dudley, 
  

  

  