﻿T. 
  DAVIDSON 
  AND 
  W. 
  KING 
  ON 
  THE 
  TBIMEEELLID.E. 
  163 
  

  

  wide. 
  As 
  the 
  shells 
  that 
  are 
  wider 
  than 
  long 
  have 
  been 
  removed 
  to 
  

   another 
  species, 
  possibly 
  the 
  fragments 
  noticed 
  belong 
  to 
  it. 
  

  

  This 
  species 
  is 
  stated 
  to 
  occur 
  in 
  the 
  Black-river 
  limestone 
  at 
  

   Fourth 
  Chutes 
  of 
  Bonne 
  Chere, 
  Pauquette's 
  rapids 
  ; 
  and 
  in 
  the 
  town- 
  

   ships 
  of 
  Stafford 
  and 
  Westmeath, 
  county 
  of 
  Renfrew, 
  Canada. 
  Its 
  

   geological 
  position 
  seems 
  to 
  be 
  about 
  the 
  horizon 
  of 
  the 
  Upper 
  

   Llandeilo 
  — 
  that 
  is, 
  below 
  the 
  Caradoc 
  formation. 
  

  

  Dinoboltjs 
  tbansverses, 
  Salter. 
  PI. 
  XVIII. 
  fig. 
  12. 
  

  

  Obolus 
  Davidsoni, 
  var. 
  transversus, 
  Dav., 
  vol. 
  i., 
  General 
  Introduc- 
  

   tion, 
  p. 
  136, 
  fig. 
  53, 
  1853 
  ; 
  Sil. 
  Brach. 
  p. 
  59, 
  pi. 
  v. 
  figs. 
  1-6, 
  

   1866. 
  

  

  Dinobolus 
  Davidsoni, 
  Dav. 
  & 
  King, 
  Report 
  of 
  Brighton 
  Meeting 
  

   of 
  Brit. 
  Assoc. 
  20th 
  August, 
  1872 
  ; 
  Annals, 
  and 
  Geol. 
  Mag. 
  of 
  

   the 
  same 
  year. 
  

  

  General 
  form 
  much 
  wider 
  than 
  long; 
  compressed. 
  Valves 
  exter- 
  

   nally 
  marked 
  by 
  fine 
  strise 
  parallel 
  to 
  their 
  margins. 
  Brachial 
  valve 
  

   thick, 
  and 
  elevated 
  in 
  the 
  umbo-cardinal 
  region 
  ; 
  thence 
  thin 
  and 
  

   flattening 
  out 
  to 
  the 
  margin 
  : 
  crescent 
  strongly 
  impressed 
  at 
  its 
  sides 
  ; 
  

   obscurely 
  impressed 
  at 
  its 
  ends 
  : 
  platform 
  depressed 
  ; 
  very 
  slightly 
  

   raised 
  at 
  its 
  margins 
  ; 
  well 
  defined 
  posteriorly 
  : 
  postmedian 
  scar, 
  p, 
  

   subrhomboidal 
  ; 
  sharply 
  differentiated 
  from 
  the 
  platform 
  scars 
  : 
  sub- 
  

   cardinal 
  scars, 
  w, 
  in 
  close 
  contact 
  with 
  the 
  latter. 
  

  

  Very 
  little 
  is 
  known 
  with 
  reference 
  to 
  this 
  species, 
  only 
  a 
  cast 
  of 
  

   the 
  interior 
  of 
  the 
  brachial 
  valve 
  having 
  been 
  found 
  : 
  it 
  exceeds 
  2| 
  

   inches 
  in 
  breadth 
  by 
  nearly 
  2 
  inches 
  in 
  length, 
  indicating- 
  a 
  large 
  

   size 
  for 
  the 
  species, 
  apparently 
  larger 
  than 
  any 
  of 
  the 
  others. 
  It 
  

   differs 
  from 
  D. 
  Davidsoni 
  in 
  being 
  wider 
  and 
  more 
  depressed 
  — 
  also 
  

   in 
  its 
  internal 
  characters, 
  as 
  denoted 
  in 
  the 
  diagnosis. 
  The 
  sides 
  

   (apparently 
  their 
  inner 
  border) 
  of 
  the 
  crescent, 
  which 
  are 
  consider- 
  

   ably 
  apart 
  from 
  the 
  lateral 
  margins 
  of 
  the 
  valves, 
  have 
  the 
  pecu- 
  

   liarities 
  characteristic 
  of 
  other 
  species, 
  but 
  still 
  more 
  exaggerated. 
  

  

  Dinobolus 
  transversus 
  occurs 
  in 
  the 
  calcareous 
  shales 
  at 
  the 
  top 
  of 
  

   the 
  Wenlock 
  limestone 
  in 
  the 
  neighbourhood 
  of 
  Dudley 
  ; 
  and 
  at 
  the 
  

   Rushall 
  canal, 
  near 
  Walsall, 
  Park 
  Hall. 
  

  

  Dinobolus 
  Woodwaedi, 
  Salter. 
  

  

  Obolus 
  Davidsoni, 
  var. 
  Woodwardi, 
  Salter, 
  MS. 
  ; 
  Dav. 
  Sil. 
  Brach. 
  

  

  p. 
  60, 
  pi. 
  v. 
  figs. 
  7, 
  8, 
  1866. 
  

   Dinobolus 
  Davidsoni, 
  Dav. 
  & 
  King, 
  Report 
  of 
  Brighton 
  Meeting 
  

  

  of 
  Brit. 
  Assoc. 
  20th 
  August, 
  1872 
  ; 
  also 
  in 
  Geol. 
  Mag., 
  and 
  the 
  

  

  Ann. 
  & 
  Mag. 
  Nat. 
  Hist, 
  of 
  the 
  same 
  year. 
  

  

  Certain 
  undetermined 
  differences 
  observable 
  in 
  an 
  imperfect 
  cast, 
  

   which 
  is 
  transversely 
  oval 
  and 
  marked 
  with 
  concentric 
  lines 
  of 
  

   growth, 
  led 
  Mr. 
  Salter 
  to 
  suggest 
  that 
  it 
  might 
  belong 
  to 
  a 
  species 
  

   distinct 
  from 
  D. 
  transversus 
  : 
  possibly, 
  however, 
  when 
  better 
  known, 
  

   it 
  may 
  prove 
  to 
  be 
  no 
  more 
  than 
  a 
  variety. 
  It 
  occurs 
  in 
  the 
  Wenlock 
  

   limestone 
  of 
  Dormington, 
  Woolhope, 
  and 
  in 
  the 
  associated 
  shales- 
  

   near 
  Dudley. 
  

  

  