﻿8 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL. 
  MUSEUM 
  vol.67 
  

  

  Anodontites, 
  because 
  of 
  its 
  form, 
  colors, 
  and 
  wide 
  prismatic 
  border, 
  

   which 
  are 
  exactly 
  like 
  those 
  of 
  Anodontites 
  patagonicus. 
  Were 
  the 
  

   portion 
  of 
  the 
  hinge 
  line 
  bearing 
  the 
  tooth 
  broken 
  away 
  one 
  would 
  

   be 
  absolutely 
  unable 
  to 
  separate 
  F. 
  fossiculifera 
  from 
  A. 
  pata- 
  

   gonicus. 
  If 
  Fossicida 
  and 
  Leila 
  be 
  valid 
  genera 
  it 
  seems 
  there 
  

   should 
  be 
  some 
  shifting 
  in 
  classification 
  in 
  order 
  to 
  bring 
  the 
  former 
  

   near 
  A. 
  patagonicus 
  and 
  the 
  latter 
  near 
  A. 
  trapesialis, 
  instead 
  of 
  

   arranging 
  Leila 
  between 
  Fossicula 
  and 
  Anodontites. 
  The 
  radiating 
  

   threads 
  do 
  not 
  show 
  well 
  in 
  any 
  of 
  the 
  four 
  specimens 
  at 
  hand, 
  but 
  

   enough 
  remains 
  to 
  tell 
  that 
  the 
  threads 
  occur 
  in 
  this 
  genus 
  and 
  that 
  

   they 
  are 
  like 
  those 
  to 
  be 
  found 
  in 
  some 
  specimens 
  of 
  Anodontites 
  

   patagonicus. 
  Plate 
  2, 
  figure 
  2, 
  represents 
  a 
  small 
  spot 
  in 
  a 
  specimen 
  

   from 
  Parana 
  River 
  (Cat. 
  No. 
  86346, 
  U.S.N.M.). 
  It 
  has 
  about 
  105 
  

   threads 
  to 
  the 
  millimeter. 
  

  

  Genus 
  LEILA 
  

  

  The 
  shells 
  of 
  this 
  genus 
  are 
  uniformly 
  large. 
  In 
  the 
  whole 
  family 
  

   Mutelidae 
  they 
  are 
  exceeded 
  in 
  size 
  by 
  only 
  one 
  species, 
  Anodontites 
  

   trapesialis 
  Lamarck, 
  with 
  which 
  perhaps 
  they 
  should 
  be 
  placed 
  in 
  

   a 
  section 
  of 
  the 
  genus 
  Anodontites, 
  or 
  perhaps 
  trapesialis 
  should 
  be 
  

   taken 
  from 
  that 
  genus 
  and 
  placed 
  in 
  the 
  genus 
  Leila. 
  Surely 
  the 
  

   shells 
  show 
  a 
  very 
  near 
  relationship 
  to 
  each 
  other. 
  The 
  radiating 
  

   threads 
  in 
  Leila 
  are 
  extremely 
  fine 
  and 
  resemble 
  those 
  of 
  the 
  African 
  

   genus 
  Spatha, 
  rather 
  than 
  those 
  usual 
  to 
  the 
  South 
  American 
  species 
  

   of 
  Mutelidae. 
  They 
  are 
  of 
  about 
  the 
  same 
  nature 
  as 
  those 
  of 
  

   Spatha 
  wahlbergi. 
  In 
  these 
  large 
  shells 
  the 
  striae 
  are 
  difficult 
  

   to 
  find 
  because 
  they 
  are 
  so 
  very 
  fine, 
  and 
  they 
  seem 
  to 
  be 
  easily 
  lost 
  

   as 
  growth 
  progresses. 
  A 
  specimen 
  of 
  Leila 
  blainvilleana 
  from 
  the 
  

   Amazon 
  River 
  (Cat. 
  No. 
  25815, 
  U.S.N.M.) 
  shows 
  the 
  fine 
  lines, 
  but 
  

   not 
  clearly 
  enough 
  to 
  be 
  photographed. 
  

  

  Genus 
  ANODONTITES 
  

  

  Plate 
  1, 
  fig. 
  1 
  ; 
  plate 
  2, 
  fig. 
  3 
  ; 
  plate 
  3, 
  figs. 
  1 
  and 
  3 
  

  

  To 
  this 
  genus 
  belong 
  the 
  larger 
  portion 
  of 
  all 
  the 
  species 
  referred 
  

   to 
  the 
  family 
  Mutelidae. 
  There 
  are 
  recognized 
  some 
  50 
  species 
  of 
  

   Anodontites. 
  They 
  have 
  been 
  divided 
  into 
  several 
  sections 
  and 
  

   groups, 
  but 
  there 
  is 
  ground 
  for 
  believing 
  that 
  further 
  study 
  will 
  

   result 
  in 
  dividing 
  this 
  genus 
  into 
  several 
  genera. 
  The 
  shells 
  now 
  

   included 
  in 
  Anodontites 
  show 
  a 
  wide 
  range 
  of 
  characteristics, 
  vary- 
  

   ing 
  in 
  form, 
  size, 
  colors, 
  weight, 
  sculpture, 
  etc. 
  For 
  instance, 
  com- 
  

   pare 
  A. 
  rotundus 
  Spix 
  with 
  A. 
  trapesialis 
  Lamarck; 
  A. 
  patagonicus 
  

   Lamarck 
  with 
  A. 
  strebeli 
  Lea, 
  and 
  any 
  of 
  these 
  with 
  A. 
  tenebricosus 
  

   Lea; 
  or 
  compare 
  A. 
  ensiformis 
  Spix 
  and 
  A. 
  falsus 
  Simpson 
  with 
  

   any 
  of 
  the 
  other 
  Anodontites. 
  The 
  genus 
  has 
  a 
  great 
  geographic 
  

   range, 
  extending 
  from 
  Mexico 
  to 
  Patagonia. 
  In 
  nearly 
  all 
  of 
  the 
  

  

  