346 M. Ogilvie Gordon — Fauna of Up]per Cassian, South Tyrol. 



Subordinate movements have readily taken place at the planes 

 where the more rigid and the more plastic rock-groups have been 

 next one another. Thus local conditions have produced local 

 modification of the more general movements due to compression 

 and cross-compression of this district in subsequent epochs of Alpine 

 upheaval. 



In addition to its use in the solution of the stratigraphy, the value 

 of an Upper Cassian fauna is in the link it adds to the Upper Trias 

 chain of faunas in South Tyrol. Its discovery and its identification 

 by me in 1893 as a transitional Cassian-Eaibl zone established, for 

 the first time in South Tyrol, a closely connected series of paleeonto- 

 logical zones traceable through Wengen-Cassian-Eaibl periods. The 

 Upper Cassian zone has therefore given important evidence of the 

 impracticability of placing a paleeontological limit between Middle 

 and Upper Alpine Trias anywhere within that series. The transition 

 from Eaibl horizons to Dachstein Dolomite in Enneberg and Ampezzo 

 also takes place quite gradually, as evidenced by species of the genus 

 Megalodus. Hence the only subdivision between Middle and Upper 

 Trias which seems natural in the ' Dolomites ' is between the Upper 

 Muschelkalk (Buchenstein strata of some authors) and the Wengen 

 series, that is, at the horizon of Triassic time, when eruptive material 

 began to be incorporated with the local sediments of that area. 

 (Cf. von Wohrmann, "Die Kaibler Schichten," 1893; Eothpletr, 

 " Querschnitt," 1894 ; Salomon, " Pal8eontographica," 1895 ; von 

 Zittel, " Zeitschrift," 1899.) 



A farther confirmation of the presence of a transitional Cassian-Eaibl 

 fauna in the ' Dolomites ' has been given by the fauna in the ' Pachy- 

 cardia Tuffs ' of the Seiser-Alpe. Geheimrath von Zittel, who made 

 the discovery, during a geological excursion with his students, that 

 these tuffs contained a large number of Eaibl forms in addition to 

 Cassian forms, has since published a short account of the faunal 

 characteristics of these tufaceous horizons at the Seiser-Alpe (von 

 Zittel, "Zeitschrift," 1899; also Eothpletz, "Zeitschrift," 1899). 

 The preliminary notes on the stratigraphy given bj' Prof. Eothpletz 

 show that these tuffs at the Seiser Alpe rest conformably upon strata 

 containing a Stuores-Cassian fauna, so that in this important feature 

 their position at the Seiser-Alpe agrees with that which I determined 

 at Falzarego Valley and other localities. The ' Cipit Limestones' 

 also occur, as blocks or irregular banks, at various horizons, in the 

 way that I described for other localities along the Buchenstein- 

 Mahlknecht area of eruptive invasions. " Along the hem of this 

 volcanic girdle communities of Corals and Echinoderms settled and 

 formed a series of small barrier reefs (Cipit Limestones), frequently 

 interrupted in their growth by fresh lavas" (aut. I.e., 1894). 



But, compared with the Falzarego Valley fauna, the ' Pachycardia- 

 tuff' fauna bears a distinct local impress. For example, just as 

 I never found Pachycardia Eaueri in the higher Eaibl horizons of 

 Falzarego Valley, so I never found Pachycardia rugosa, the leading 

 fossil of the Pachycardia tuffs, in the Upper Cassian zone of 

 Falzarego Valley. Both may be there, as my personal collection 



