Yol.  49.]  ANNIVERSARY  ADDRESS  OF  THE  PRESIDENT  12 3 
conclusion  involves  tlie  proving  of  a  negative,  viz.  that  the  two 
characteristic  oysters  never  appear  together  either  in  the  Oxford  or 
the  Kim.eridge  Clay.  At  all  events  such  an  occurrence  must  be 
extremely  rare,  and  if  there  are  cases  quoted  they  may  possibly  be 
capable  of  some  other  explanation.  We  may  therefore  admit  that 
clays  which  contain  both  these  forms  of  oyster  are  likely  to  be  of 
Corallian  age. 
It  is  not,  perhaps,  to  be  expected  that  the  Geological  Survey 
should  lay  down  the  lines  of  a  third  clay  in  Lincolnshire,  and  so 
separate  the  Oxford  and  Kimeridge  Clays,  where  no  beds  of  the  usual 
Corallian  type  supervene.  Nevertheless  the  map  which  illustrates 
Mr.  Roberts’s  paper  is  a  very  useful  piece  of  work,  and  eminently 
characteristic  of  that  conscientious  and  painstaking  geologist, 
whose  untimely  death  we  all  so  much  deplore. 
Turning  our  attention  now  from  Lincolnshire  to  Wiltshire,  but 
still  dealing  with  the  Upper  Jurassic,  I  must  remind  you  of  an 
interesting  account  of  a  well-sinking  at  Swindon  given  by  Messrs. 
H.  B.  Woodward  and  E.  T,  Newton.  One  cannot  help  being  struck 
with  the  great  development  of  Oxfordian  beds  at  this  spot,  com¬ 
pletely  reversing  the  conditions  which  prevail,  for  instance,  in  the 
Weymouth  district,  and  considerably  exceeding  the  limits  assigned 
to  the  Oxford  Clay  by  Prestwich  at  the  city  of  Oxford.  There  are 
probably  not  many  places  in  England  where  the  Oxford  Clay  and 
Kellaways  Rock  together  attain  a  thickness  of  572  feet. 
Callovian  Ammonites  occur  in  the  lowest  beds,  which  for  a 
moderate  thickness  exhibit  the  sandy  conditions  of  the  ordinary 
Kellaways  Rock.  These  are  succeeded  by  220  feet  of  clays  con¬ 
taining  Ammonites  of  the  ornatus-grouip ,  in  company  with  many 
other  species.  The  Cephalopod  fauna  of  these  beds  is  evidently  rich, 
when  so  many  species  can  be  quoted  from  so  limited  an  amount  of 
material.  The  results,  however,  are  fairly  in  accord  with  what  we 
know  of  Oxfordian  beds  generally  where  the  lower  zones,  as  in  the 
upper  part  of  the  Kelloway  Rock  of  Scarborough,  are  full  of  Ammo¬ 
nites  of  many  species.  It  is  somewhat  singular,  however,  that  the 
well-known  Corallian  Am.  plicatilis ,  should  occur  in  these  ornatus - 
clays.  The  Upper  Oxfordian  is  290  feet  thick ;  this  roughly  repre¬ 
sents  the  corclatus- zone,  and  it  is  very  poor  in  species  as  compared 
with  the  lower  beds,  just  as  we  see  is  the  case  in  Yorkshire. 
The  Corallian  beds  in  the  Swindon  sinking  were  found  to  be  feebly 
developed,  and  one  wonders  what  has  become  of  the  massive  Rag  of 
Wootton  Basset  only  a  few  miles  away.  There  is  not  much  to  be 
