518 
THE  BAJOCIAN  OF  THE  SHERBORNE  DISTRICT. 
[Nov.  1893. 
In  the  memoirs  of  Munier-Chalmas  and  Hang  the  identifica¬ 
tion  of  Ammonite-species  is  evidently  very  exact.  Herein  lies  the 
value  01  their  works  for  purposes  of  correlation  ;  and  much  might 
le  said  concerning  the  remarkable  correspondence  in  the  faunal 
succession  in  the  Trench  Alps,  in  Normandy,  and  in  Dorset.  In  this 
connexion  the  Table  on  the  opposite  page  should  be  useful ;  it  com¬ 
pares  the  faunal  succession  according  to  these  authors  and  myself. 
Conclusion. 
By  way  of  conclusion  I  would  make  a  few  additional  remarks 
concerning  the  proposed  term  ‘  hemera.’  It  must  be  particularly 
understood  that  it  is  used  m  a  chronological  sense  as  a  subdivision 
0  an  age.  Here  I  would  take  occasion  to  state  what  seems  to 
be  a  paradox  that  species  may  occur  together  in  the  rocks,  yet  such 
occurrence  is  no  proof  that  they  were  contemporaneous.  If  the 
species  have  not  been  proved  to  be  successive  in  other  places,  then 
occurrence  in  the  same  bed  may  be  assumed  to  indicate 
that  they  were  contemporaneous  until  such  proof  be  forthcoming 
It  is,  however,  only  negative  evidence.  If  they  have  been  proved 
to  be  successive  species,  then  their  occurrence  together  only  shows 
that  the  deposit  in  which  they  are  embedded  accumulated  very 
slowly  Had  this  been  rightly  understood  we  should  have  been 
spared  the  stress  that  has  been  laid  upon  a  so-called  intermixture 
ot  zonal  species ;  though  I  must  say  that  too  often  an  investigation 
of  such  supposed  intermixture  proves  it  a  fiction  due  to  inaccurate 
palaeontology  or  incorrect  geology. 
.  ^  be  remai>ked  that  much  depends  on  the  interpretation 
given  to  ‘  together.’  However,  in  this  paper,  in  many  cases— 
especially  as  regards  Halfway  House  and  Sherborne— it  will  be  seen 
that  species  which  occur  together  in  a  thin  band  of  rock  at  the  one 
place  are  proved  to  be  not  contemporaneous  when  the  very  much 
greater  accumulation  of  strata  at  the  other  place  is  examined.  The 
following  diagram  will  show  how  this  can  be  :  — 
II. 
A  and  B 
In  palaeo-hiolog}7  it  is  of  the  utmost  importance  to  have  recorded  a 
fact  such  as  that,  at  certain  places,  B  always  marks  a  distinctly  higher 
horizon  than  A.  If  they  are  only  labelled  as  being  from  the  same 
zone,  those  who  are  unacquainted  with  the  strata  in  the  field  may 
he  forgiven  for  supposing  that  B  may  have  lived  before  A.  Several 
mistakes  in  genealogy  have  arisen  from  this  cause.  If,  however, 
there  be  a  record  that  B  lived  during  a  later  hemera  than  A — that 
when  A  and  B  occur  together  it  is  only  because  of  very  slow 
deposition  during  the  same  length  of  time  as  when  they  occur  widely 
separated — such  mistakes  can  be  avoided. 
