20 
THE  WENGEIT  AED  ST.  CASSTAH  STEATA.  [Eeb.  1893. 
The  fossiliferous  beds  of  Prelongei  continue  in  a  general  easterly 
direction  with  the  strike,  although  often  lost  sight  of  under  the 
long  lines  of  blocks  tumbled  from  Sett  Sass  Berg,  and  pass  under 
the  lens- shaped  dolomitic  rock  of  the  Bichthofen  Biff.  They  form 
the  slight  hollow  eroded  between  the  Biff  and  the  mass  of  blocks 
on  the  Castello  Wiese,  and  are  occasionally  traced  on  the  banks  of 
streams  flowing  eastward  to  the  Yalparola  stream.  The  series  of 
beds,  Bos.  10  to  8  in  the  Prelongei  section,  are  however  cut  off  on 
the  Castello  Wiese  by  an  east-and-west  line  of  fault,  demonstrable 
in  two  ways  : — 
(1)  The  light-grey  shales  with  Posidonomya ,  n.  sp.  (the  species 
differs  slightly  from  Posidonomya  wengensis\  which  form  a  constant 
horizon  in  the  St.  Cassian  strata  of  this  district  of  Prelongei  (see 
Section  1,  Bo.  16,  and  Section  2,  Bo.  10),  pass  over  the  ridge  and 
are  traced  beneath  the  blocks  on  the  Castello  Wiese.  This  is  true 
for  other  beds,  such  as  the  ashy  series,  the  ferruginous  marls,  and 
the  beds  of  hard  Cipit  Limestone.  One  after  another,  these  beds 
are  cut  off,  and  beds  of  a  different  palaeontological  and  lithological 
character  appear  in  their  place. 
(2)  The  beds  thus  cut  off  have  in  the  neighbourhood  of  the  line 
of  fault  a  strike  B.  50°  W.,  and  the  beds  faulted  against  them 
strike  B.  25°-30°  E.,  the  two  systems  meeting  almost  at  right  angles 
to  one  another. 
The  succession  of  beds  in  the  section,  although  interrupted  by 
this  fault-line,  fall  into  the  main  groups  as  before : — 
St.  Cassian  Beds .  . 
Wengen  Beds . .  . . 
Buchenstein  Beds 
Sett  Sass  and 
Monte  Sief. 
f  Bos.  14-9. 
*  #  * 
%  *  * 
Bos.  8-2. 
.Bo.  1. 
Castello. 
Bos.  14-11  (in  part).  ^ 
*  * 
Bo.  9  a. 
Bo.  8  a. 
Bo.  8-2. 
Bo.  1.  v 
H  O 
•  i— i  rH 
«  fi 
;  O  cl 
Vrt 
<a  ig 
The  Wengen  and  St.  Cassian  strata  of  all  three  sections  may  be 
further  subdivided  into  well-marked  zones,  based  both  on  palaeontolo¬ 
gical  and  stratigraphical  evidence.  A  marked  feature  in  the  Prelongei 
district  is  the  occurrence  of  thickly-bedded  and  sometimes  massive 
limestones  at  the  base  of  the  St.  Cassian  Series.  They  have  all  the 
appearance  of,  and  agree  palaeontologically  with,  the  Cipit  Limestones 
first  recognized  by  Bichthofen  on  the  Seisser  Alpe.  In  several 
traverses  which  I  made  over  St.  Cassian  and  Wengen  strata  exposed 
in  various  localities  between  the  Seisser  Alpe  and  the  district  of 
Prelongei,  I  observed  such  Cipit  Limestones  always  at  the  horizon 
where  the  St.  Cassian  fauna  begins  to  appear,  and  where  the 
commonly  occurring  Wengen  fossils  begin  to  lessen  in  number. 
I  have  therefore  accepted  this  horizon  as  the  best  stratigraphical 
limit  between  the  Wengen  and  St.  Cassian  Beds. 
