﻿so 
  PROCKEDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIKTr. 
  

  

  Eocene. 
  In 
  concluding 
  this 
  preliminary 
  stateraent 
  I 
  wish 
  to 
  thank 
  

   my 
  friend 
  Mr, 
  B. 
  B. 
  Woodward, 
  F.L.S., 
  for 
  some 
  valuable 
  suggestions 
  

   during 
  the 
  prosecution 
  of 
  my 
  studies 
  on 
  this 
  shell. 
  

  

  Eaetomya, 
  gen. 
  nov. 
  

  

  Diagnosis. 
  — 
  Shell 
  inequilateral, 
  obliquely 
  gibbose, 
  thin, 
  con- 
  

   centrically 
  and 
  irregularly 
  plicate, 
  striated 
  and 
  wrinkled; 
  dorsal 
  

   areas 
  not 
  defined; 
  anterior 
  side 
  deep, 
  long, 
  oblique, 
  depresso- 
  

   concave, 
  posterior 
  region 
  short,^ 
  marginally 
  compressed, 
  reflected, 
  

   slightly 
  gaping; 
  umbonal 
  areas 
  arched, 
  summits 
  opisthogyrous, 
  

   incurved, 
  oblique, 
  laterally 
  approximate 
  but 
  distant 
  with 
  age, 
  the 
  

   right 
  elevated 
  above 
  the 
  left; 
  left 
  valve 
  with 
  strong 
  hinge-plate 
  

   furnished 
  with 
  a 
  horizontally 
  projecting 
  triangular 
  chondrophore 
  

   marginally 
  grooved 
  each 
  side, 
  deeply 
  excavated 
  anteriorly 
  and 
  

   striate 
  within, 
  succeeded 
  by 
  an 
  antero-marginal 
  sulcus, 
  the 
  posterior 
  

   side 
  liaving 
  a 
  wider 
  marginal 
  sulcus 
  to 
  receive 
  the 
  laminar 
  tooth 
  of 
  

   the 
  other 
  valve; 
  right 
  valve 
  provided 
  with 
  a 
  shallow 
  oval 
  chondro- 
  

   phore 
  set 
  back 
  in 
  the 
  sub-umbonal 
  cavity, 
  obliquely 
  ridged 
  posteriorly 
  

   to 
  connect 
  with 
  the 
  postero-latcral 
  groove 
  of 
  the 
  left 
  chondrophore, 
  

   followed 
  by 
  a 
  narrow 
  sulcus, 
  a 
  posterior 
  laminar 
  tooth, 
  and 
  a 
  

   widely 
  depressed 
  dorsal 
  furrow; 
  cardinal 
  teeth 
  absent 
  in 
  both 
  

   valves; 
  pallial 
  impression 
  widely 
  indented 
  by 
  a 
  nearly 
  circular 
  

   sinus 
  ; 
  adductor 
  scars 
  unequal, 
  posterior 
  more 
  or 
  less 
  normal, 
  

   anterior 
  narrow 
  and 
  elongate. 
  

  

  Type. 
  — 
  Lovellia 
  schweinfurthi, 
  Mayer-Eymar, 
  from 
  the 
  Eocene 
  

   (Upper 
  Mokattam 
  Beds) 
  of 
  Egypt. 
  

  

  liemarh. 
  — 
  The 
  new 
  shell 
  agrees 
  with 
  the 
  mactroid 
  genus 
  liaela,^ 
  

   in 
  most 
  external 
  characters, 
  but 
  differs 
  internally 
  by 
  possessing: 
  

   (1) 
  dissimihir 
  chondrophores, 
  tlie 
  left 
  being 
  triangular 
  and 
  projecting 
  

   outwards, 
  while 
  the 
  right 
  is 
  triangularly 
  ovate, 
  vertical, 
  and 
  well 
  

   within 
  the 
  sub-umbonal 
  region 
  ; 
  (2) 
  no 
  cardinal 
  teeth 
  ; 
  (3) 
  a 
  large 
  

   rounded 
  pallial 
  sinus. 
  The 
  chief 
  external 
  distinction 
  concerns 
  the 
  

   summits 
  or 
  umbones, 
  which 
  instead 
  of 
  being 
  opposite 
  each 
  other 
  and 
  

   nearly 
  touching 
  as 
  in 
  liaeta 
  are 
  laterally 
  approximate 
  but 
  becoming 
  

   more 
  or 
  less 
  distant 
  with 
  age, 
  that 
  of 
  the 
  right 
  valve 
  being 
  always 
  

   in 
  front 
  of 
  the 
  other 
  and 
  rather 
  more 
  elevated, 
  such 
  as 
  is 
  observable 
  

   in 
  Corbula 
  gallica, 
  C. 
  exarata, 
  etc., 
  from 
  the 
  European 
  Eocene 
  

   deposits. 
  In 
  its 
  projecting 
  character 
  the 
  left 
  chondrophore 
  resembles 
  

   that 
  present 
  in 
  Mija, 
  but 
  instead 
  of 
  merging 
  with 
  the 
  postero-dorsal 
  

   margin 
  as 
  in 
  that 
  genus 
  it 
  radiates 
  outwards, 
  with 
  the 
  other 
  

   extended 
  elements 
  of 
  the 
  hinge-plate, 
  from 
  a 
  point 
  immediately 
  

   beneath 
  the 
  umbo. 
  A 
  similarly 
  projecting 
  chondrophore 
  is 
  also 
  

   apparent 
  in 
  members 
  of 
  the 
  Corbulidae, 
  otherwise 
  such 
  shells 
  as 
  well 
  

   as 
  Mya 
  are 
  quite 
  distinct 
  from 
  the 
  present 
  genus. 
  

  

  In 
  Raeta 
  the 
  chondrophores 
  are 
  of 
  similar 
  construction 
  and 
  

  

  ^ 
  In 
  this 
  respect 
  resembling 
  the 
  genera 
  Raeta, 
  Niicula, 
  Pisidium, 
  etc. 
  

  

  ^ 
  According 
  to 
  Dr. 
  Dall 
  the 
  true 
  systematic 
  position 
  of 
  Raeta 
  is 
  still 
  uncertain, 
  

  

  since 
  its 
  soft 
  parts 
  are 
  unknown 
  : 
  Trans. 
  Wagner 
  Free 
  Inst. 
  Sci. 
  

  

  Philadelphia, 
  vol. 
  iii, 
  pt. 
  iv, 
  1898, 
  p. 
  907. 
  

  

  