﻿SALTER 
  BTTDLEIGH 
  SALTERTON 
  FOSSILS. 
  295 
  

  

  angles 
  rounded, 
  the 
  centre 
  not 
  at 
  all 
  depressed. 
  The 
  surface 
  is 
  not 
  

   known, 
  but 
  the 
  strise 
  seem 
  to 
  have 
  been 
  very 
  fine. 
  A 
  few 
  concentric 
  

   ridges 
  of 
  growth 
  show 
  on 
  this 
  valve, 
  which 
  do 
  not 
  interfere 
  with 
  the 
  

   regular 
  convexity 
  of 
  the 
  valve. 
  The 
  hinge-area 
  is 
  not 
  so 
  wide 
  as 
  

   the 
  shell. 
  

  

  The 
  interior 
  is 
  characteristic, 
  and 
  unlike 
  any 
  British 
  species 
  I 
  am 
  

   acquainted 
  with, 
  except 
  0. 
  lata, 
  Sowerby. 
  The 
  hinge-teeth 
  are 
  

   strictly 
  parallel, 
  and 
  rather 
  converge 
  instead 
  of 
  diverge 
  ; 
  and 
  the 
  

   cardinal 
  process 
  is 
  exactly 
  as 
  long 
  as 
  the 
  teeth. 
  The 
  three 
  extend 
  

   the 
  same 
  distance, 
  and, 
  being 
  very 
  prominent, 
  form 
  in 
  the 
  cast 
  a 
  deep 
  

   circumscribed 
  depression, 
  beneath 
  which 
  the 
  quadripartite 
  muscular 
  

   scars 
  are 
  very 
  distinct. 
  The 
  muscles 
  include 
  a 
  circular 
  space, 
  

   divided 
  by 
  a 
  thick 
  prominent 
  median 
  ridge, 
  which 
  extends 
  the 
  whole 
  

   length 
  of 
  the 
  muscles. 
  The 
  upper 
  pair 
  are 
  only 
  half 
  the 
  size 
  of 
  the 
  

   lower. 
  The 
  shoulders, 
  formed 
  in 
  the 
  cast 
  by 
  the 
  hollow 
  spaces 
  out- 
  

   side 
  the 
  teeth, 
  are 
  very 
  square, 
  and 
  rise 
  close 
  to 
  the 
  narrow 
  hinge 
  - 
  

   area, 
  thereby 
  indicating 
  that 
  the 
  teeth 
  and 
  the 
  shell 
  itself 
  about 
  the 
  

   hinge 
  are 
  very 
  thin. 
  These 
  internal 
  characters 
  are 
  found 
  to 
  be 
  

   very 
  distinctive 
  in 
  species 
  of 
  Orthis. 
  

  

  PoRAMBONITES, 
  Sp. 
  PI. 
  XVII. 
  fig. 
  9. 
  

  

  This 
  is 
  certainly 
  a 
  Porambonites 
  (see 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  ix. 
  

   p. 
  8), 
  but 
  I 
  do 
  not 
  wish 
  to 
  name 
  the 
  species 
  from 
  a 
  single 
  spe- 
  

   cimen. 
  

  

  7. 
  Spirifer 
  antiquissimus, 
  spec. 
  nov. 
  PI. 
  XVII. 
  figs. 
  10-12. 
  

  

  To 
  all 
  appearance 
  this 
  is 
  a 
  Spirifer, 
  and 
  I 
  am 
  compelled 
  from 
  

   the 
  structure 
  o£ 
  tKe 
  toott 
  ic 
  do«««iV»« 
  i+ 
  «« 
  «vi«k. 
  But 
  w« 
  

   British 
  species 
  of 
  Orthis 
  (0. 
  spir 
  if 
  'eroides), 
  in 
  the 
  Caradoc 
  Sandstone, 
  

   which 
  exactly 
  resembles 
  it 
  in 
  outline 
  and 
  convexity. 
  Otherwise 
  I 
  

   might 
  believe, 
  with 
  my 
  friend 
  M. 
  de 
  Verneuil, 
  that 
  it 
  was 
  a 
  Devonian 
  

   fossil 
  introduced 
  into 
  these 
  beds. 
  It 
  would 
  seem 
  that 
  there 
  is 
  at 
  

   least 
  one 
  allied 
  species 
  of 
  Spirifer 
  in 
  the 
  French 
  Silurian 
  deposits 
  — 
  

  

  8. 
  Bavidis, 
  Rouault. 
  

  

  "We 
  have 
  three 
  specimens 
  of 
  the 
  dorsal 
  (smaller) 
  valve, 
  which 
  is 
  

   1 
  inch 
  and 
  y^ths 
  wide, 
  and 
  not 
  so 
  long 
  as 
  broad, 
  being 
  only 
  1 
  inch 
  

   and 
  T 
  \)th 
  in 
  length, 
  with 
  a 
  straight 
  hinge-line 
  as 
  wide 
  as 
  the 
  shell. 
  

   The 
  form 
  is 
  semioval 
  and 
  regularly 
  convex, 
  except 
  a 
  rather 
  broad 
  

   dorsal 
  fold, 
  which 
  projects 
  a 
  good 
  deal 
  beyond 
  the 
  front 
  margin 
  and 
  

   interrupts 
  the 
  otherwise 
  regular 
  semioval 
  contour. 
  

  

  The 
  sinus 
  is 
  about 
  one-third 
  the 
  whole 
  width 
  at 
  the 
  front, 
  and 
  

   thence 
  tapers 
  regularly 
  to 
  the 
  hinge 
  ; 
  it 
  is 
  abruptly 
  raised 
  and 
  then 
  

   flattened 
  above, 
  and 
  both 
  it 
  and 
  the 
  rest 
  of 
  the 
  shell 
  are 
  regularly 
  

   covered 
  by 
  radiating 
  ribs, 
  about 
  four 
  in 
  the 
  space 
  of 
  a 
  line, 
  which 
  

   are 
  uniform 
  from 
  the 
  beak 
  to 
  the 
  front, 
  not 
  interrupted 
  by 
  ridges 
  of 
  

   growth, 
  nor 
  interlined 
  by 
  other 
  ribs. 
  

  

  The 
  internal 
  cast 
  shows 
  the 
  teeth 
  widely 
  divaricating 
  at 
  an 
  angle 
  

   of 
  130°, 
  and 
  without 
  the 
  strong 
  central 
  cardinal 
  process 
  which 
  would 
  

   be 
  present 
  if 
  it 
  were 
  an 
  Orthis. 
  The 
  muscular 
  impressions 
  are 
  

   elongate, 
  instead 
  of 
  quadrate. 
  The 
  median 
  septum 
  extends 
  two- 
  

  

  vol. 
  xx. 
  — 
  part 
  i. 
  x 
  

  

  