﻿NEWTON: 
  ON 
  AXODOyTA 
  BECKLESI, 
  N.SP., 
  ETC. 
  117 
  

  

  partial 
  internal 
  characters, 
  may 
  now 
  be 
  pronounced 
  as 
  belonging 
  to 
  

   the 
  true 
  ZTnio. 
  Some 
  of 
  these 
  latter 
  shells 
  actually 
  bear 
  manuscript 
  

   names 
  written 
  by 
  Mantell 
  and 
  Beckles, 
  indicating 
  that 
  they 
  were 
  

   regarded 
  as 
  Anodonta. 
  The 
  characters 
  of 
  the 
  species 
  under 
  descrip- 
  

   tion 
  are 
  spread 
  over 
  two 
  or 
  three 
  specimens 
  in 
  different 
  states 
  of 
  

   preservation, 
  although 
  unfortunately 
  without 
  details 
  of 
  the 
  hinge, 
  as 
  

   none 
  have 
  been 
  successfully 
  developed 
  in 
  that 
  region. 
  An 
  interesting 
  

   point 
  of 
  this 
  shell 
  is 
  its 
  general 
  resemblance 
  to 
  Anodonta 
  propatoris 
  of 
  

   C. 
  A. 
  White 
  from 
  the 
  Upper 
  Cretaceous 
  (Laramie 
  Beds) 
  rocks 
  of 
  the 
  

   United 
  States, 
  and 
  also 
  to 
  some 
  modern 
  forms 
  living 
  in 
  North 
  American 
  

   rivers, 
  especially 
  that 
  known 
  as 
  A, 
  Steivartiana 
  of 
  Reeve 
  (Conchologia 
  

   Iconica, 
  1870, 
  pi. 
  xxxiii, 
  species 
  133), 
  thus 
  showing 
  the 
  persistence 
  

   of 
  one 
  particular 
  type 
  of 
  this 
  genus 
  from 
  Wealden 
  to 
  modern 
  times. 
  

   But 
  although 
  exhibiting 
  a 
  similarity 
  of 
  contour, 
  the 
  Wealden 
  shell 
  is 
  

   much 
  more 
  compressed 
  and 
  larger, 
  whilst 
  the 
  ornamentation 
  appears 
  

   to 
  separate 
  it 
  from 
  anything 
  seen 
  either 
  in 
  a 
  recent 
  or 
  fossil 
  form. 
  

   The 
  radial 
  striations 
  are 
  better 
  exhibited 
  on 
  a 
  specimen 
  displaying 
  

   a 
  dorsal 
  view 
  of 
  both 
  valves 
  in 
  the 
  closed 
  condition. 
  It 
  is 
  possible 
  

   that 
  such 
  markings 
  represent 
  the 
  position 
  of 
  the 
  original 
  colour-streaks 
  

   which 
  may 
  have 
  been 
  a 
  feature 
  of 
  the 
  valves 
  during 
  the 
  life 
  of 
  the 
  

   mollusc, 
  as 
  is 
  common 
  among 
  recent 
  Afiodonta 
  and 
  the 
  shells 
  of 
  the 
  

   Unionidse 
  generally. 
  Probably 
  the 
  outer 
  shell-structure 
  is 
  not 
  present, 
  

   in 
  which 
  case 
  the 
  ornamentation 
  seen 
  would 
  occur 
  just 
  below 
  it, 
  

   because 
  in 
  the 
  modern 
  A. 
  cygnea 
  radial 
  striations 
  are 
  observable 
  on 
  

   the 
  nacreous 
  layer 
  which 
  lies 
  beneath 
  the 
  outer 
  shelly 
  covering. 
  The 
  

   species 
  is 
  in 
  other 
  ways 
  well 
  characterized, 
  especially 
  in 
  connexion 
  

   with 
  the 
  marked 
  angulai'ity 
  of 
  the 
  lateral 
  aspect 
  of 
  the 
  valves, 
  the 
  

   posterior 
  region 
  being 
  strikingly 
  developed. 
  

  

  The 
  specific 
  name 
  proposed 
  is 
  in 
  memory 
  of 
  a 
  former 
  geologist, 
  

   S. 
  H. 
  Beckles, 
  F.B.S., 
  who 
  was 
  one 
  of 
  the 
  earlier 
  authorities 
  on 
  the 
  

   geology 
  and 
  fossils 
  of 
  the 
  deposits 
  in 
  the 
  neighbourhood 
  of 
  Hastings. 
  

  

  Occurrence. 
  — 
  Examples 
  of 
  this 
  species 
  are 
  found 
  in 
  the 
  Tairlight 
  

   Clays 
  ', 
  which 
  is 
  the 
  basal 
  division 
  of 
  the 
  Wealden 
  beds 
  near 
  Hastings, 
  

   having 
  been 
  obtained 
  from 
  between 
  Ecclesbourne 
  and 
  Fairlight 
  Glen. 
  

   They 
  occur 
  in 
  grey-coloured 
  sandstones, 
  reddish 
  ironstone, 
  and 
  softish 
  

   drab 
  clays, 
  being 
  sometimes 
  accompanied 
  on 
  the 
  same 
  matrix 
  by 
  

   fragmentary 
  plant 
  remains. 
  

  

  EXPLANATION 
  OF 
  PLATE 
  I. 
  

  

  Anodonta 
  Becklesi, 
  n.sp. 
  

  

  Wealden 
  (Fairlight 
  Clays). 
  Near 
  Hastings. 
  

  

  Fig. 
  1. 
  Specimen 
  with 
  extended 
  valves 
  on 
  matrix, 
  showing 
  excavated 
  posterior 
  

  

  ridges, 
  radial 
  lineations, 
  etc. 
  [P. 
  Eufford 
  Coll., 
  British 
  Museum, 
  

  

  L. 
  6244.] 
  

  

  ,, 
  2. 
  Eight 
  valve, 
  of 
  a 
  suhquadrate 
  form, 
  attached 
  to 
  matrix. 
  [P. 
  Eufford 
  

  

  Coll., 
  British 
  Museum, 
  L. 
  6228.] 
  

   ,, 
  3. 
  Dorsal 
  view 
  of 
  an 
  example 
  with 
  closed 
  valves, 
  exhihiting 
  smooth 
  umhoual 
  

   regions 
  and 
  wide 
  posterior 
  area. 
  [S. 
  H. 
  Beckles 
  Coll., 
  British 
  Museum, 
  

   L. 
  8384.] 
  

   ,, 
  4. 
  Details 
  of 
  sculpture-markings 
  as 
  observed 
  on 
  specimen 
  represented 
  by 
  

   Fig. 
  3, 
  X 
  3, 
  showing 
  the 
  disjointed 
  character 
  of 
  the 
  filiform 
  radial 
  

   striations. 
  

   Note. 
  — 
  The 
  figures 
  on 
  this 
  Plate 
  are 
  of 
  the 
  natural 
  size, 
  with 
  the 
  exception 
  of 
  

   Fig. 
  4, 
  which 
  is 
  a 
  magnification. 
  

  

  VOL. 
  IX. 
  — 
  jvxE, 
  1910. 
  9 
  

  

  