﻿363 
  

  

  ON 
  THE 
  MODIFICATIONS 
  IN 
  FOKM 
  OF 
  THE 
  UPPER 
  TERTIAHY 
  

   LACUSTRINE 
  SHELLS 
  OF 
  THE 
  ISLAND 
  OF 
  COS, 
  AS 
  FIRST 
  

   OBSERVED 
  BY 
  EDWARD 
  FORBES 
  AND 
  T. 
  A. 
  B. 
  SPRATT. 
  

  

  By 
  K. 
  BuLLEN 
  Newton, 
  F.G.S. 
  

  

  Bead 
  Wi 
  June, 
  1911. 
  

  

  PLATE 
  XII. 
  

  

  An 
  abundant 
  freshwater 
  molluscan 
  fauna 
  characterizing 
  the 
  Upper 
  

   Tertiary 
  deposits 
  of 
  Southern 
  Europe 
  and 
  Asia 
  Minor 
  has 
  long 
  proved 
  

   a 
  fascinating 
  study 
  to 
  the 
  palseoconchologist. 
  To 
  German 
  writers 
  we 
  

   are 
  mainly 
  indebted 
  for 
  our 
  present 
  knowledge 
  of 
  the 
  subject, 
  the 
  beds 
  

   having 
  been 
  described 
  as 
  consisting 
  of 
  alternating 
  sands 
  and 
  clays 
  

   which 
  frequently 
  rise 
  to 
  considerable 
  elevations, 
  as 
  in 
  Slavonia, 
  

   Austria, 
  where 
  they 
  reach 
  more 
  than 
  2,000 
  feet. 
  The 
  beds 
  have 
  been 
  

   divided 
  into 
  two 
  groups 
  — 
  an 
  upper, 
  known 
  as 
  Paludinen- 
  Schichten, 
  from 
  

   tlie 
  occurrence 
  of 
  the 
  characteristic 
  shell 
  Viviparus 
  or 
  Paludina, 
  and 
  

   a 
  lower, 
  termed 
  Congerien- 
  Schichten 
  on 
  account 
  of 
  the 
  frequently 
  

   found 
  Peleeypod 
  genus 
  Congeria. 
  The 
  upper 
  group 
  is 
  included 
  in 
  

   the 
  Pliocene 
  system, 
  whilst 
  the 
  other 
  belongs 
  to 
  the 
  uppermost 
  part 
  

   of 
  the 
  Miocene, 
  known 
  as 
  the 
  Pontian 
  stage 
  of 
  that 
  period. 
  

  

  Perhaps 
  the 
  most 
  familiar 
  memoir 
  on 
  the 
  subject, 
  so 
  far 
  at 
  least 
  as 
  

   Slavonia 
  is 
  concerned, 
  was 
  that 
  issued 
  by 
  Neumayr 
  & 
  Paul 
  in 
  1875 
  

   under 
  the 
  title 
  of 
  "Die 
  Congerien 
  und 
  Paludinenschichten 
  Slavoniens 
  

   uud 
  deren 
  Faunen 
  ; 
  ein 
  Beitrag 
  zur 
  Descendenz-Theorie 
  " 
  (Abhandl. 
  

   k. 
  k. 
  Geol. 
  Reichs., 
  vol. 
  vii, 
  pt. 
  iii, 
  pis. 
  i-x, 
  1875). 
  In 
  this 
  work 
  the 
  

   authors 
  recognized 
  three 
  horizons 
  as 
  forming 
  the 
  Paludinen- 
  Schichten, 
  

   w 
  hich 
  were 
  characterized 
  by 
  distinctive 
  forms 
  of 
  Viviparus 
  ( 
  = 
  Paludina). 
  

   The 
  first 
  or 
  oldest 
  contained 
  smooth 
  species 
  of 
  the 
  genus, 
  accompanied 
  

   by 
  equally 
  smooth 
  varieties 
  of 
  Unio 
  ; 
  the 
  second 
  horizon 
  showed 
  

   carinated 
  species 
  associated 
  with 
  thick 
  forms 
  of 
  Unio 
  without 
  ornament 
  ; 
  

   and 
  the 
  third 
  exhibited 
  carinate 
  or 
  tubercled 
  varieties 
  occurring 
  in 
  

   company 
  with 
  highly 
  ornamented 
  Unio. 
  The 
  viviparoid 
  shells 
  

   exhibiting 
  such 
  mutations 
  were 
  regarded 
  as 
  having 
  orijiinated 
  from 
  

   the 
  smooth 
  form 
  of 
  Viviparus 
  Neummjri, 
  belonging 
  to 
  the 
  most 
  ancient 
  

   of 
  the 
  deposits, 
  the 
  immediate 
  ancestor 
  of 
  which 
  species 
  was 
  stated 
  by 
  

   the 
  authors 
  to 
  be 
  V. 
  achatinoides 
  of 
  Deshayes, 
  originally 
  described 
  

   from 
  the 
  Miocene 
  (Pontian 
  Beds) 
  formation 
  of 
  the 
  Crimea. 
  

  

  The 
  views 
  here 
  briefly 
  enunciated, 
  and 
  which 
  had 
  an 
  important 
  

   bearing 
  on 
  the 
  theoiy 
  of 
  evolution, 
  brought 
  a 
  great 
  reputation 
  to 
  the 
  

   authois, 
  who 
  ever 
  since 
  have 
  been 
  quoted 
  as 
  the 
  original 
  exponents 
  of 
  

   so 
  interesting 
  a 
  discovery. 
  

  

  Although 
  somewhat 
  late 
  in 
  the 
  day 
  to 
  call 
  in 
  question 
  the 
  originality 
  

   of 
  these 
  particular 
  statements, 
  it 
  may 
  surprise 
  mnny 
  students 
  to 
  learn 
  

   that 
  the 
  phenomenon 
  involved 
  in 
  Neumayr 
  & 
  Paul's 
  work 
  had 
  been 
  

   observed 
  many 
  years 
  previously 
  by 
  the 
  great 
  English 
  naturalists 
  

   Professor 
  Edward 
  Forbes 
  and 
  Lieutenant 
  (afterwards 
  Admiral) 
  T. 
  A. 
  B. 
  

   Spratt 
  in 
  connexion 
  with 
  another 
  area 
  of 
  Southern 
  Europe, 
  situated 
  in 
  

   the 
  Eastern 
  Mediterranean, 
  where 
  the 
  geological 
  conditions 
  were 
  of 
  

  

  