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MR.  S.  S.  BTTCKMAN  ON  THE  BAJOCIAN  [NoV.  l893> 
Lytoceras  of  the  jurense- group  ”  ;  also  Erycites,1  and  what 
should  be  very  interesting,  species  of  Sonninia. 
C.  “  The  upper  horizon  represents  only  the  base  of  the  beds  of 
Ludwigia  concava . The  middle  and  upper  beds  .  .  . 
are  wanting  in  Normandy.  .  .  .  The  numerous  forms  of  Lud¬ 
wigia  derived  from  Ludwigia  Murchison  <2  2  abound  ( pullulent ) 
at  this  horizon.  .  .  .  Ludwigia  concava,  var.  v-scripta  (Buckm.), 
L.  cornu,  Buckm.,  L.  aperta  (Buckm.),  L.  decipiens  (Buckm.), 
L.  rudis,  Buckm.  Sonninia  and  Zurcheria  are  also  repre¬ 
sented  .” 
II.  “  The  beds  of  Ludwigia  v-scripta  .  .  .  support  a  stratum  remark¬ 
able  for  the  important  change  in  the  genera  of  the  cephalopoda. 
Numerous  Witchellice ,  some  Poecilomorphi,  Lissocerata,  and 
Coelocerata,  all  mostly  new  species,  are  found  at  this  horizon."’ 
III.  “  The  strata  with  Sonninia  patella ,  S.  propinquans ,  .  .  .  and 
Coeloceras  Sauzei”  follow. 
IV.  “Beds  with  Witchellia  Romani,  Sonninia  deltafalcata ,  and 
S.  furticarinata  are  not  known  in  Normandy.” 
In  comparison  with  what  I  had  noted  in  Dorset,  as  shown  in 
this  paper,  it  will  be  seen  that  the  following  correlations  may  be 
made :  — 
I. — A .  Murchisonce  hemera. 
B .  Bradfordensis  hemera. 
C .  Concavi  hemera,  pars. 
II .  Witchellice  sp.  hemera. 
III  .  Sauzei  hemera. 
IV  .  Unnoticed. 
Tt  is  interesting  to  observe  that  Munier-Chalmas  speaks  of 
middle  and  upper  beds  of  c  Ludwigia  concava .’  Not  improbabty  his 
upper  beds  equal  the  “strata  of  the  discitce  hemera;  ”  but  I  have 
made  no  separation  into  two  lower  beds.  It  is,  however,  very  evi¬ 
dent  that  much  attention  will  have  to  be  given  to  these  lower  strata. 
Comparatively  speaking,  it  is  but  recently  that  the  fossils  have  been 
collected  with  anything  like  precision  as  to  their  horizons  ;  yet  far 
greater  exactitude  in  noting  these  horizons  is  evidently  required. 
In  the  Cotteswolds  it  is  easy  to  note  horizons  with  the  greatest 
1  Munier-Chalmas  calls  attention  to  the  occurrence  of  this  genus,  which  has 
usually  been  considered,  as  he  rightly  observes,  peculiar  to  the  Mediterranean 
borders.  Species  of  the  genus  from  this  country  have  been  known  to  me  for 
some  twelve  years,  and  I  was  under  the  impression  that  I  had  called  attention 
to  their  occurrence.  Such  was,  in  fact,  the  case;  but  the  statement  did  not 
make  its  appearance  in  print.  The  MS.  was  presented  in  1891  to  the  British 
Association  for  the  Advancement  of  Science;  but  in  the  ‘short  abstract’ 
published  (see  Geol.  Mag.  for  1891,  p.  502)  if  was  not  possible  to  advance 
this  and  other  scientific  facts. 
2  From  my  friend  Dr.  Haug  I  know  that  Prof.  Munier-Chalmas  has 
always  held  this  opinion  concerning  the  relationship  of  Ammonites  of  the 
concavus- type.  I  took  a  different  view  in  my  Monograph,  but  a  study  of  the 
very  large  series  of  specimens  contained  in  the  collection  of  Mr.  Darell 
Stephens,  F.G.S.,  convinced  me  some  little  while  back  that  I  was  in  error.  I 
had  evidently  been  deceived  by  morphological  equivalents. 
It  seemed  to  me  not  to  be  advisable  to  make  this  confession  until  I  was  in  a 
position  to  give  the  fullest  details  at  the  end  of  the  first  volume  of  my  Monograph  ; 
but  in  justice  to  Prof.  Munier-Chalmas  I  cannot  omit  the  present  opportunity. 
I  may  say  that  I  have  also  been  in  error  concerning  the  derivation  of  Hyper- 
lioceras ;  this  genus  is  also  closely  connected  by  descent  with  Ludwigia. 
