﻿SALTER 
  — 
  BUDLEIGH 
  SALTERTON 
  FOSSILS. 
  299 
  

  

  series 
  of 
  thin 
  edentulous 
  Silurian 
  shells, 
  which 
  Professor 
  M'Coy 
  

   has 
  arranged 
  provisionally 
  in 
  his 
  genus 
  Anodontopsis. 
  There 
  is 
  no 
  

   certainty 
  that 
  Pseudaooinus 
  is 
  related 
  to 
  Ilodiola, 
  although 
  Ano- 
  

   dontopsis 
  belongs 
  to 
  that 
  group 
  ; 
  and 
  the 
  presumption 
  is 
  against 
  it. 
  

   It 
  may 
  quite 
  as 
  likely 
  be 
  an 
  edentulous 
  form 
  of 
  Arcadce. 
  

  

  Thin, 
  edentulous, 
  convex, 
  with 
  prominent 
  umbones 
  and 
  a 
  strong 
  

   posterior 
  carinated 
  ridge 
  ; 
  beaks 
  anterior 
  ; 
  no 
  lunette. 
  Surface 
  

   smooth 
  or 
  only 
  concentrically 
  striate. 
  

  

  Types, 
  P. 
  (Anodontopsis) 
  securiformis, 
  M'Coy, 
  and 
  P. 
  trigonus, 
  here 
  

   described. 
  

  

  1x^7. 
  Pseitdaxinijs 
  trigoxus, 
  spec. 
  nov. 
  PI. 
  XV. 
  fig. 
  6. 
  

  

  Eleven 
  lines 
  long, 
  and 
  ten 
  high 
  ; 
  the 
  depth 
  of 
  the 
  united 
  convex 
  

   valves 
  being 
  7-^- 
  lines. 
  Beaks 
  very 
  prominent, 
  almost 
  gibbous, 
  from 
  

   which 
  a 
  strong 
  carina 
  runs 
  to 
  the 
  posterior 
  angle. 
  Anterior 
  side 
  

   very 
  convex, 
  rounded, 
  somewhat 
  oblique, 
  with 
  no 
  lunette 
  or 
  depres- 
  

   sion 
  beneath 
  the 
  beak 
  ; 
  posterior 
  side 
  obliquely 
  truncate, 
  pointed, 
  

   concave. 
  Surface 
  with 
  fine 
  concentric 
  striae. 
  

  

  -*""" 
  Hippomta, 
  gen. 
  nov. 
  (Fam. 
  Mytilid^j.) 
  

  

  A 
  curious 
  shell, 
  whose 
  affinities 
  with 
  the 
  MytiUdce 
  I 
  do 
  not 
  think 
  

   doubtful, 
  but 
  which 
  may 
  probably 
  indicate 
  still 
  more 
  closely 
  the 
  

   relation 
  between 
  this 
  group 
  and 
  the 
  Arcadce. 
  In 
  no 
  living 
  genera 
  

   allied 
  to 
  Mod 
  tola 
  is 
  there 
  so 
  extensive 
  a 
  development 
  of 
  the 
  foot 
  

   and 
  byssus 
  as 
  must 
  have 
  been 
  here 
  present, 
  to 
  give 
  rise 
  to 
  the 
  great 
  

   horseshoe-shaped 
  sinus 
  on 
  the 
  anterior 
  part 
  of 
  the 
  ventral 
  aspect. 
  

   The 
  typical 
  Arcades 
  (Byssoarca) 
  have 
  a 
  somewhat 
  similar 
  character. 
  

   Yet 
  this 
  is 
  a 
  thin 
  shell, 
  with 
  close 
  umbones 
  and 
  no 
  trace 
  of 
  cardinal 
  

   area, 
  while 
  the 
  obscurity 
  in 
  our 
  specimen 
  of 
  any 
  muscular 
  scars 
  

   prevents 
  a 
  close 
  comparison 
  with 
  the 
  genera 
  of 
  either 
  group. 
  I 
  

   cannot 
  help 
  suspecting 
  that 
  Modiolarca 
  is 
  its 
  nearest 
  ally 
  *. 
  The 
  

   name 
  may 
  be 
  understood 
  to 
  have 
  only 
  a 
  general 
  signification, 
  and 
  

   not 
  to 
  indicate 
  any 
  close 
  relations 
  with 
  My 
  a. 
  The 
  shell 
  does 
  not 
  

   gape 
  at 
  either 
  end, 
  except 
  for 
  the 
  foot 
  and 
  byssus. 
  

  

  A 
  gibbous 
  shell, 
  with 
  anterior 
  inflated 
  close 
  beaks, 
  a 
  long 
  cardi- 
  

   nal 
  edge, 
  but 
  no 
  area, 
  not 
  gaping 
  at 
  either 
  end, 
  the 
  anterior 
  side 
  

   short, 
  rounded, 
  and 
  separated 
  by 
  a 
  strong 
  sinus 
  from 
  the 
  inflated 
  

   posterior 
  ridge 
  and 
  slope 
  ; 
  surface 
  with 
  lines 
  of 
  growth 
  only, 
  no 
  

   radii. 
  Anterior 
  margin, 
  for 
  nearly 
  half 
  the 
  length 
  of 
  the 
  shell, 
  

   strongly 
  incurved, 
  and 
  widely 
  open 
  for 
  the 
  passage 
  of 
  a 
  large 
  ovate 
  

   byssus, 
  which 
  was 
  probably 
  very 
  short, 
  horny, 
  and 
  disk-like. 
  

  

  ^S 
  8. 
  Hippomta 
  rixgens, 
  sp. 
  nov. 
  PI. 
  XV. 
  fig. 
  7. 
  

  

  An 
  inch 
  and 
  a 
  quarter 
  long 
  by 
  ten 
  lines 
  high, 
  and 
  depth 
  of 
  united 
  

   valves 
  fully 
  one 
  inch. 
  The 
  valves 
  are 
  obliquely 
  trapezoidal-ovate, 
  

   the 
  posterior 
  margin 
  obliquely 
  truncate 
  above, 
  the 
  anterior 
  equally 
  

   truncate 
  below 
  and 
  parallel 
  to 
  it. 
  A 
  regular 
  gibbosity 
  marks 
  the 
  

   posterior 
  slope, 
  greatest 
  in 
  the 
  middle 
  of 
  the 
  shell, 
  which 
  is 
  decidedly 
  

  

  * 
  See 
  Woodward. 
  Ann. 
  Nat. 
  Hist. 
  1856. 
  

  

  