﻿

  V°l- 
  53-] 
  0F 
  THE 
  CHALK 
  rock. 
  37# 
  

  

  Elbthalgeb. 
  in 
  Sachsen,' 
  pt. 
  ii. 
  (1873) 
  p. 
  55, 
  pi. 
  xvi. 
  f. 
  78 
  ; 
  Fritsch, 
  ' 
  Stud, 
  im 
  

   Gebiete 
  der 
  bohm. 
  Kreidef'oraiat. 
  IV. 
  Die 
  Teplitzer 
  Scbicbten 
  ' 
  (1889), 
  p. 
  79, 
  fig. 
  63 
  ; 
  

   Favre, 
  'Moll. 
  Foss. 
  de 
  la 
  Craie 
  des 
  Envir. 
  de 
  Lemberg' 
  (1869), 
  p. 
  125, 
  pi. 
  xii. 
  

   f. 
  15 
  & 
  16.] 
  

  

  Remarks. 
  — 
  A 
  specimen, 
  consisting 
  of 
  an 
  internal, 
  and 
  part 
  of 
  an 
  

   external 
  mould, 
  agrees 
  with 
  A. 
  Geinitzi 
  in 
  form, 
  but 
  differs 
  in 
  

   possessing 
  rather 
  finer 
  and 
  more 
  numerous 
  ribs. 
  It 
  is 
  probably 
  the 
  

   form 
  figured 
  by 
  Sowerby 
  as 
  Byssoarca 
  marullensis 
  l 
  from 
  the 
  Chalk 
  

   of 
  Kent. 
  Size 
  of 
  specimen 
  from 
  Cuckhamsley 
  : 
  length 
  (approxi- 
  

   mate) 
  = 
  23mm.; 
  height=ll 
  mm. 
  

  

  A. 
  Geinitzi 
  occurs 
  in 
  the 
  Planer-Kalk 
  of 
  Strehlen 
  (Saxony), 
  in 
  

   the 
  Teplitz 
  Beds 
  of 
  Bohemia, 
  etc. 
  

  

  Distribution. 
  — 
  Chalk 
  Eock 
  of 
  Cuckhamsley. 
  

  

  Akca 
  sp. 
  (PI. 
  XXVII. 
  fig. 
  4.) 
  

  

  Description. 
  — 
  Shell 
  oblique, 
  elongate, 
  anteriorly 
  very 
  short 
  and 
  

   rounded. 
  Posterior 
  margin 
  oblique, 
  somewhat 
  rounded. 
  Umbones 
  

   sharp. 
  Surface 
  with 
  concentric 
  lines 
  of 
  growth 
  ; 
  and 
  with 
  radiat- 
  

   ing 
  ribs 
  extending 
  from 
  the 
  umbo 
  to 
  the 
  posterior 
  margin. 
  Size 
  : 
  

   length 
  = 
  13 
  mm. 
  ; 
  height=6 
  mm. 
  

  

  Remarks. 
  — 
  This 
  species 
  is 
  at 
  present 
  known 
  by 
  one 
  specimen 
  

   only. 
  It 
  resembles 
  Area 
  strehlensis, 
  Geinitz, 
  from 
  the 
  Planer-Kalk 
  

   of 
  Strehlen, 
  but 
  in 
  that 
  form 
  the 
  shell 
  is 
  less 
  oblique, 
  and 
  the 
  

   surface 
  is 
  generally 
  smooth, 
  except 
  on 
  the 
  anterior 
  part 
  which 
  is 
  

   marked 
  with 
  radiating 
  ribs. 
  

  

  Distribution. 
  — 
  Chalk 
  Eock 
  of 
  Cuckhamsley 
  (Montagu 
  Smith 
  

   Collection). 
  

  

  Genus 
  Limopsis, 
  Sassi, 
  1827. 
  

  

  Limopsis 
  sp. 
  (PI. 
  XXVII. 
  figs. 
  7 
  & 
  8.) 
  

  

  Description. 
  — 
  Shell 
  small, 
  oval, 
  convex, 
  a 
  little 
  oblique, 
  wider 
  

   than 
  long 
  ; 
  margins 
  of 
  valves 
  not 
  crenulate. 
  Casts 
  show 
  fine 
  radi- 
  

   ating 
  striae, 
  sometimes 
  crossed 
  by 
  a 
  few 
  shallow 
  concentric 
  furrows. 
  

   Size: 
  length=8 
  mm., 
  height 
  = 
  7 
  mm. 
  

  

  Remarks. 
  — 
  At 
  present 
  this 
  species 
  is 
  known 
  only 
  from 
  the 
  casts, 
  

   so 
  that 
  a 
  complete 
  description 
  cannot 
  yet 
  be 
  given 
  ; 
  it 
  seems, 
  how- 
  

   ever, 
  quite 
  distinct 
  from 
  the 
  other 
  forms. 
  I 
  have 
  not 
  been 
  able 
  to 
  

   make 
  out 
  the 
  hinge-plate 
  in 
  a 
  satisfactory 
  manner, 
  and 
  it 
  is 
  possible- 
  

   that 
  this 
  species 
  may 
  really 
  belong 
  to 
  Axinosa. 
  

  

  Affinities. 
  — 
  Homer's 
  2 
  Pectunculus 
  planus 
  is 
  similar 
  to 
  this 
  species, 
  

   but 
  the 
  valves 
  are 
  flatter 
  and 
  the 
  umbones 
  less 
  prominent. 
  

  

  Distribution. 
  — 
  Chalk 
  Eock 
  of 
  Cuckhamsley. 
  

  

  1 
  Sowerby 
  (non 
  d'Orbigny) 
  in 
  F. 
  Dixon's 
  ' 
  Geol. 
  Sussex' 
  (1850), 
  p. 
  355 
  & 
  

   pi. 
  xxviii. 
  fig. 
  11. 
  I 
  have 
  not 
  been 
  able 
  to 
  find 
  the 
  original 
  of 
  Sowerby's 
  

   figure. 
  

  

  2 
  ' 
  Die 
  Verstein. 
  des 
  norddeutsch. 
  Kreidegeb.' 
  1841, 
  p. 
  69 
  & 
  pi. 
  viii. 
  fig. 
  24. 
  

  

  

  