﻿1863.] 
  JENKINS 
  JAVAN 
  FOSSILS. 
  61 
  

  

  19. 
  Pythina 
  Semperi, 
  spec. 
  nov. 
  PL 
  VII. 
  figs. 
  8 
  a, 
  8 
  6. 
  

  

  Shell 
  small, 
  transversely 
  elongated, 
  equilateral, 
  ovato- 
  triangular 
  ; 
  

   flexuous, 
  having 
  a 
  deep 
  triangular 
  depression 
  in 
  the 
  middle 
  of 
  the 
  

   left 
  valve, 
  whilst 
  the 
  right 
  valve 
  is 
  scarcely 
  depressed 
  in 
  that 
  region; 
  

   the 
  shell 
  is 
  also 
  twisted 
  laterally 
  towards 
  the 
  left 
  in 
  the 
  anterior 
  

   region. 
  Anterior 
  margin 
  of 
  the 
  valves 
  rounded, 
  posterior 
  more 
  

   tapering 
  ; 
  dorsal 
  margin 
  descending 
  posteriorly 
  : 
  ventral 
  edge 
  of 
  

   the 
  left 
  valve 
  rather 
  sinuous 
  ; 
  that 
  of 
  the 
  right 
  valve 
  concave, 
  as 
  if 
  

   a 
  lenticular 
  piece 
  had 
  been 
  cut 
  out 
  of 
  the 
  longer 
  side 
  of 
  a 
  semi-oval 
  

   dish. 
  Umbones 
  very 
  small. 
  Surface 
  of 
  the 
  shell 
  concentrically 
  

   striated, 
  especially 
  on 
  the 
  right 
  valve. 
  In 
  consequence 
  of 
  the 
  left 
  

   valve 
  being 
  so 
  much 
  more 
  twisted 
  than 
  the 
  right, 
  the 
  anterior 
  margin 
  

   of 
  the 
  latter 
  appears 
  to 
  be 
  produced 
  downwards 
  to 
  some 
  extent; 
  and 
  

   when 
  the 
  valves 
  are 
  closed, 
  there 
  is 
  a 
  narrowly 
  lanceolate 
  gape 
  in 
  

   the 
  middle 
  of 
  the 
  ventral 
  region. 
  

  

  This 
  little 
  shell 
  approaches 
  most 
  nearly 
  to 
  Pythina 
  peculiaris, 
  A. 
  

   Adams, 
  a 
  species 
  inhabiting 
  the 
  coasts 
  of 
  Ceylon, 
  and 
  remarkable 
  

   for 
  its 
  lateral 
  twist 
  and 
  deeply 
  sinuous 
  ventral 
  margin. 
  I 
  have 
  

   named 
  it 
  after 
  my 
  friend 
  Dr. 
  Otto 
  Semper, 
  of 
  Altona, 
  to 
  whom 
  I 
  am 
  

   indebted 
  for 
  assistance 
  in 
  comparing 
  this 
  and 
  other 
  shells 
  with 
  

   specimens 
  in 
  Mr. 
  Cuming's 
  collection. 
  

  

  Dimensions. 
  — 
  Length 
  -^ 
  inch, 
  breadth 
  -^ 
  inch. 
  

  

  Matrix. 
  — 
  This 
  species 
  was 
  obtained 
  from 
  the 
  interior 
  of 
  the 
  single 
  

   specimen 
  of 
  Pyrula 
  Javanis. 
  

  

  20. 
  Cytherea, 
  sp. 
  

  

  A 
  single 
  mutilated 
  cast 
  of 
  a 
  species 
  of 
  this 
  genus, 
  with 
  a 
  small 
  

   portion 
  of 
  the 
  shell 
  still 
  adhering 
  to 
  the 
  dorsal 
  region, 
  exists 
  in 
  M. 
  

   de 
  Groot's 
  collection. 
  It 
  is 
  broadly 
  oval, 
  almost 
  flat 
  at 
  the 
  sides, 
  

   and 
  very 
  inequilateral 
  ; 
  the 
  anterior 
  margin 
  is 
  broken 
  away, 
  but 
  was 
  

   probably 
  almost 
  semicircular; 
  and 
  the 
  posterior 
  margin, 
  though 
  

   quite 
  as 
  defective, 
  appears 
  to 
  have 
  been 
  more 
  or 
  less 
  pointed. 
  

   There 
  is 
  just 
  enough 
  of 
  the 
  shell 
  left 
  to 
  show 
  that 
  the 
  ligamental 
  

   area 
  was 
  narrowly 
  lanceolate 
  in 
  form 
  ; 
  but 
  the 
  lunule 
  has 
  disappeared. 
  

  

  Many 
  species 
  of 
  Cytherea 
  approach 
  one 
  another 
  very 
  closely 
  in 
  

   general 
  form, 
  so 
  that 
  it 
  is 
  difficult 
  to 
  arrive 
  at 
  a 
  satisfactory 
  con- 
  

   clusion 
  as 
  to 
  the 
  affinities 
  of 
  a 
  mutilated 
  cast. 
  The 
  nearest 
  in 
  

   form 
  to 
  this 
  species 
  is, 
  perhaps, 
  Cytherea 
  erycina, 
  Lam. 
  ; 
  but 
  that 
  

   shell 
  is 
  concentrically 
  sulcated, 
  while 
  this 
  appears 
  to 
  be 
  smooth. 
  

  

  Matrix. 
  — 
  The 
  cast 
  is 
  composed 
  of 
  a 
  reddish 
  marl 
  containing 
  

   grains 
  of 
  sand. 
  

  

  21. 
  Tellina, 
  sp. 
  

  

  Three 
  internal 
  casts 
  referable 
  to 
  this 
  genus 
  are 
  orbicular, 
  slightly 
  

   ventricose, 
  and 
  almost 
  equilateral 
  ; 
  anterior 
  margins 
  rounded 
  ; 
  poste- 
  

   rior 
  slightly 
  angular, 
  in 
  consequence 
  of 
  two 
  ridges 
  extending 
  radiately 
  

   from 
  near 
  the 
  umbones 
  to 
  the 
  margin 
  : 
  the 
  stronger 
  ridge 
  is 
  the 
  

   more 
  anterior 
  one; 
  it 
  is 
  slightly 
  curved, 
  and 
  is 
  preceded 
  in 
  the 
  left 
  

   valve 
  by 
  a 
  wedge-shaped 
  depression. 
  The 
  surfaces 
  of 
  the 
  casts 
  are 
  

  

  