38  MISS  OGILVIE  ON  THE  WENGEN  AND  [Feb.  1 893, 
area  of  the  Seisser  Alpe  and  underlying  the  marls  containing 
St.  Cassian  fossils. 
Mojsisovics  quotes  ‘  Pachycardia- tuffs  ’  in  Wengen  strata  from 
other  districts,  referring  them  to  a  horizon  immediately  above  the 
plant-bearing  sandstones  (‘  Dolomit-Riffe,’  pp.  55  and  56). 
Emmrich,  in  1840,  found  certain  fossils  in  the  higher  marls,  and 
on  a  later  visit  he  obtained  a  great  number  and  recognized  them  as 
a  thoroughly  representative  ‘  Stuores  "VYiese  ’  (?’.  e.  St.  Cassian)  fauna. 
The  fossils  however  occur,  comparatively  speaking,  seldom  ;  some  of 
the  characteristic  species  in  Emmrich’s  collection  are  :  Cidaris  bacvs- 
lifera ,  C.  Poemeri ,  C.  Buchii ,  G.  trigona,  C.  dorsata,  C.  decorata , 
C.  jiexuosa ;  Encrinus  varians,  E.  cassianus ,  etc. ;  many  Terebratulce, 
Koninckincc  Leonhardti ;  Cardita  crenata,  Nucula  lineata,  and  many 
gasteropods.  Emmrich  says,  referring  to  the  Stuores  fauna : — “  The 
agreement  was  complete ;  even  their  general  appearance  and  their 
mode  of  occurrence  were  the  same.” 
In  other  words,  as  a  general  conclusion  from  the  above  sections, 
the  St.  Cassian  strata  of  the  Seisser  Alpe  correspond  only  with  a 
part  of  the  St.  Cassian  strata  of  Stuores  ;  the  richly  fossiliferous 
zones  on  the  ridge  of  Prelongei  and  below  Sett  Sass  are  not  present 
on  the  Seisser  Alpe. 
Another  feature  which  is  at  least  worthy  of  mention  here  is 
the  occurrence  of  the  fossiliferous  marls  and  Cipit  Limestones  on 
the  Seisser  Alpe,  interbedded  with  ashy  rocks ;  this  is  exactly 
how  those  fossiliferous  horizons  are  found  which  I  was  enabled 
to  distinguish  in  the  Prelongei  and  Stuores  district  as  Lower 
St.  Cassian,  and  the  ashy,  less  fossiliferous  portion  of  Middle  or 
4  Stuores  ’  St.  Cassian. 
Richthofen  called  the  strata  of  the  Seisser  Alpe  “  sedimentary 
tuffs  with  interbedded  St.  Cassian  Limestones  and  Cipit  Limestones.” 
This  is  analogous  to  the  Northern  Tyrol  contemporaneous  series — 
namely,  the  “  Partnach  marls  and  shales  with  interstratified  beds 
of  St.  Cassian  Limestone.” 1 
Mojsisovics  maps  all  the  strata  on  the  Seisser  Alpe  as  Wengen 
Beds.  While  it  is  impossible  to  draw  any  but  an  arbitrary  limit 
between  the  complex  of  Wengen  and  St.  Cassian  Beds  in  Southern 
Tyrol,  I  believe  a  clearer  conception  of  the  Upper  Triassic  succession 
will  be  gained  by  grouping  these  fossiliferous  marls  and  lime¬ 
stones  as  a  St.  Cassian  Series  in  which  (at  least  throughout  the  wide 
district  from  Schlern  to  the  Diirrenstein)  St.  Cassian  fossils  form  the 
bulk  of  the  fauna,  while  retaining  the  name  of  Wengen  Beds  for 
the  thick  ashy  series  underlying  them,  with  a  remarkably  limited 
fauna  and  interrupted  by  dykes  and  flows  of  augite-porphyry.  The 
occurrence  of  Posidonomya  wengensis  (which  is  quoted  even  from 
the  Raibl  Beds  in  the  Esino  district)  in  the  St.  Cassian  Series,  or, 
conversely,  the  occurrence  of  Cidaris  dorsata  and  a  few  other 
forms  of  higher  range  in  beds  of  Wengen  age,  need  not  preclude 
a  convenient  subdivision  of  the  whole  complex  into  the  two  main 
1  See  Gumbel  (op.  cit.  1873) :  the  ‘  St.  Cassian  strata  ’  include  a  great  part  of 
the  ‘  sedimentary  tuffs  ’  of  Richthofen. 
