M. Ogilvie Gordon — Fauna of Upper Cassian, South Tyrol. -341 



■Tyrol, ill the Upper Raibl zone (von Wohrmann, loc. cit., N. Tyrol, 

 1889, p. 250). 



Cassianella decussata and Cucallcsa impressa are present in the 

 Schlern Plateau strata, which von Wohrmann regards as con- 

 teraporaneous with the 'Upper Cardita ' or 'Lower Raibl' series 

 in North Tyrol.^ Opinions differ regarding the absolute identity of 

 the two species Myophorta decussata and Myophoriopis Uneata, in 

 the Falzarego fauna, with the types described by von Wohrmann 

 at Schlern Plateau, but the affinity is certainly close. Myophorta (?) 

 solitaria has, according to Dr. Bittner, nearest resemblance to a Raibl 

 form, M., sp. Toinmasi. The GervilUas and Pedens are genera which 

 are relatively exceedingly rare in the Stuores-Cassian zone, but here, 

 as in Raibl strata, they are of common occurrence and comprise 

 a few species identical with, or closely related to, Raibl species. 



Thus, the close examination which the Cortina Laraellibranchs 

 have now undergone has served to prove that the evidence which. 

 I gave ill 1893 of an Upper Cassian or Cassian-Raibl transition 

 2one was well-founded. Previously to 1893 the only intermediate 

 Lamellibranch fauna known in South Tyrol between the Stuores- 

 dassian zone and the typical Torer Raibl zone was the Schlern 

 Plateau fauna, but a paleeoutological gap existed between it and the 

 ■Stuores-Cassian zone. 



With regard to the Gastropods in the foregoing list of the Upper 

 Cassian fossils in Falzarego Valley, the majority of the species are 

 identical with Cassian species. This is natural, since the Stuores- 

 Cassian fauna is characterized by the extraordinary number of small 

 ^Gastropod species and individuals, whereas the Raibl fauna is 

 characterized by a greater number of Lamellibranchs in proportion 

 to the number of Gastropod species. As a local feature it may 

 be noted that certain species, e.g. Neritina imitans and Scalaria 

 ornata, are present in relatively far greater number of individuals 

 in the Falzarego area than in the Stuores Meadowlantl. More 

 important as a sign of transition is the occurrence in large number 

 of individuals of two species, Nerilopsis decussata and armafa, which 

 are common both to the Stuores-Cassian zone (in small number) and 

 to the Schlern Plateau and other Raibl faunas. Ptycliostoma pleuro- 

 tomoides- is a species numerously represented in the Upper Cassian 

 zone in Falzarego Valley and at Heilig-Kreuz, and is one which 

 continues in Raibl horizons. 



Another interesting feature in connection with the Gastropods 

 is, that several species are identical with species found in the 

 Marmolata-Kalk or calcareo-dolomitic facies south of this area, and 

 that the beds of dolomitic limestone which immediately overlie 

 the Falzarego tuffs are locally full of Gastropod fossils. The 

 transitional Cassian-Raibl relations of the other groups call for 

 less remark. Amongst the Brachiopods, AmphicUna scitula, amongst 



1 von Wohrmann, " Die Raibler Schichteu," m. Uebersichtstabelle : Jalirb. k.k. 

 Reichs., 1893, p. 768. 



2 See Kittl, "Die Gastropoden der Schicliten von St. Cassian der Siid-Alpiuen 

 Trias" : loc. cit., pp. 157-8. 



