﻿V°l- 
  53.] 
  OF 
  THE 
  CHALK 
  EOCK. 
  391 
  

  

  distinguished 
  from 
  C. 
  ligeriensis 
  by 
  its 
  more 
  quadrate 
  form, 
  the 
  short 
  

   anterior 
  part 
  of 
  the 
  shell, 
  and 
  the 
  larger 
  posterior 
  part. 
  The 
  type 
  

   of 
  quadrata 
  is 
  a 
  more 
  convex 
  shell 
  than 
  ligeriensis. 
  

  

  The 
  species 
  under 
  consideration 
  differs 
  from 
  C. 
  regularis 
  in 
  the 
  

   umbones 
  being 
  more 
  oblique 
  and 
  the 
  posterior 
  margin 
  more 
  trun- 
  

   cated. 
  

  

  Distribution. 
  — 
  England 
  : 
  Chloritic 
  Marl 
  of 
  Chard 
  ; 
  Chalk 
  Rock 
  of 
  

   Morgan's 
  Hill 
  near 
  Devizes, 
  Cuckhamsley, 
  and 
  Luton 
  cutting. 
  

   France 
  : 
  Cenomanian 
  of 
  Rouen 
  ; 
  zone 
  of 
  Pccten 
  asper 
  at 
  Savigny 
  ; 
  

   zone 
  of 
  Ammonites 
  laticlavus 
  at 
  Blanc-Nez. 
  Switzerland 
  : 
  ' 
  Gres 
  

   vert 
  superieur 
  ' 
  of 
  Ste. 
  Croix. 
  Saxony 
  : 
  Cenomanian 
  Planer 
  of 
  

   Plauen 
  ; 
  Brongniarti 
  Quader 
  Sandstone 
  of 
  Posta, 
  etc. 
  ; 
  Planer-Kalk 
  

   of 
  Strehlen 
  and 
  Weinbohla. 
  Bohemia 
  : 
  "Weissenberg, 
  Malnitz, 
  and 
  

   Iser 
  Beds. 
  — 
  Bavaria 
  : 
  Regensburg 
  Beds. 
  

  

  Aectica? 
  equistjlcata, 
  sp. 
  nov. 
  (PL 
  XXVIII. 
  figs. 
  6-8.) 
  

  

  Description. 
  — 
  Shell 
  moderately 
  convex, 
  subquadrate, 
  oblique 
  ; 
  

   umbones 
  pointed, 
  rather 
  anterior. 
  Shell 
  rather 
  thick, 
  ornamented 
  

   with 
  numerous 
  regular, 
  parallel, 
  concentric 
  grooves 
  — 
  about 
  15 
  in 
  

   10 
  mm. 
  Hinge 
  unknown. 
  Adductor-impressions 
  well 
  marked. 
  

   Approximate 
  size 
  : 
  length 
  = 
  32 
  mm. 
  ; 
  height=29 
  mm. 
  

  

  Remarks. 
  — 
  This 
  species 
  is 
  imperfectly 
  known 
  at 
  present, 
  but 
  

   since 
  the 
  ornamentation 
  appears 
  to 
  be 
  quite 
  distinct 
  I 
  have 
  ventured 
  

   to 
  give 
  it 
  a 
  specific 
  name. 
  There 
  are 
  seven 
  examples 
  of 
  it 
  in 
  the 
  

   Montagu 
  Smith 
  Collection, 
  six 
  being 
  internal 
  casts. 
  

  

  Distribution. 
  — 
  Chalk 
  Rock 
  of 
  Cuckhamsley. 
  

  

  Genus 
  Teapezitjm:, 
  Megerle 
  v. 
  Miihlfeldt, 
  1811. 
  

   Trapezium 
  teapezoidale 
  (Romer), 
  1841. 
  (PI. 
  XXVIII. 
  figs. 
  9 
  & 
  10.) 
  

  

  1841. 
  Crassatella 
  trapezoidalis, 
  F. 
  A. 
  Komer, 
  ' 
  Die 
  Verstein. 
  des 
  norddeutsch. 
  

   Kreidegeb.' 
  p. 
  74, 
  pi. 
  ix, 
  f. 
  22 
  ; 
  1846. 
  A. 
  dArcbiac, 
  Mem. 
  Soc. 
  geol. 
  France, 
  ser. 
  2, 
  

   vol. 
  ii. 
  p. 
  302. 
  

  

  1849. 
  Cyprina 
  trapezoidalis, 
  H. 
  B. 
  Geinitz, 
  ' 
  Das 
  Quadersandst. 
  in 
  Deutschl.' 
  

   p. 
  158 
  (partim); 
  1873. 
  H. 
  B. 
  Geinitz, 
  'Das 
  Elbthalgebirge 
  in 
  Sacbsen,' 
  Palseonto- 
  

   grapbica, 
  vol. 
  xx. 
  pt. 
  i. 
  p. 
  229, 
  pl. 
  1. 
  f. 
  6 
  (?f. 
  5). 
  

  

  1850. 
  Cypricardia 
  trapezoidalis, 
  A. 
  d'Orbigny, 
  ' 
  Prodr. 
  de 
  Pal.' 
  vol. 
  ii. 
  p. 
  240 
  ; 
  

   1889? 
  E. 
  Holzapfel, 
  'Die 
  Mollnsken 
  der 
  Aacbener 
  Kreide,' 
  Palaeontograpbica, 
  

   vol. 
  xxxv. 
  p. 
  179. 
  

  

  Description. 
  — 
  Shell 
  inflated, 
  trapezoidal, 
  anteriorly 
  short 
  and 
  

   rounded, 
  posteriorly 
  elongate 
  and 
  angular. 
  Ventral 
  margin 
  slightly 
  

   curved, 
  nearly 
  parallel 
  to 
  the 
  hinge-line. 
  Posterior 
  margin 
  nearly 
  

   straight, 
  forming 
  an 
  obtuse 
  angle 
  with 
  the 
  hinge-margin. 
  Umbones 
  

   much 
  curved, 
  reaching 
  almost 
  to 
  the 
  end 
  of 
  the 
  hinge-line. 
  A 
  

   sharp 
  carina, 
  gently 
  curved, 
  extends 
  from 
  the 
  umbo 
  to 
  the 
  posterior 
  

   angle, 
  and 
  cuts 
  off 
  a 
  slightly 
  concave 
  and 
  triangular 
  area. 
  Surface 
  

   with 
  concentric 
  lines. 
  

  

  Remarks. 
  — 
  This 
  is 
  a 
  very 
  rare 
  species 
  in 
  the 
  Chalk 
  Rock 
  ; 
  all 
  the 
  

   specimens 
  seen 
  are 
  casts, 
  but 
  one 
  shows 
  a 
  small 
  fragment 
  of 
  shell. 
  

   The 
  type 
  is 
  stated 
  by 
  Romer 
  to 
  have 
  come 
  from 
  the 
  Pliiner-Kalk 
  of 
  

   Strehlen 
  ; 
  but 
  Geinitz 
  has 
  never 
  found 
  the 
  species 
  in 
  that 
  locality. 
  

  

  