6 Miss M. M. Ogikie — Coral in the "Dolomites/' 



strata with volcauic and marly beds whicli takes place along this 

 volcanic zone is therefore perfectly comprehensible in the light of 

 every-day facts of deposition. There is no need to call the massifs 

 of Scblern, Eosengarten, Latemar, Marmolata, etc., " Coral Reefs," 

 merely because a thin line of heteropic division may be ti'aced 

 between these two areas of Triassic rock in South Tyrol. More- 

 over, the local recurrence of volcanic activity during a prolonged 

 period would explain the continuance of different conditions in 

 adjoining districts. While a simple interpretation such as the above 

 would explain one of the main features of Triassic geology in South 

 Tyrol, it may be objected that it would not apply within the volcanic 

 district itself, for it is in Enneberg and Groden, more than in any 

 other part of South Tyrol, that the curious suddenness of the 

 " Eeefs " strikes the eye. 



As I have said in a previous paper,^ every member of the Triassic 

 succession in South Tyrol presents variations in its thickness when 

 followed from place to place. More especially is this true of the 

 beds from Muschelkalk to Dachstein Dolomite. The names Cassian, 

 Wengen, and Buchenstein mark different horizons in a series of 

 volcanic lavas, ashy and tufaceous marls, calcareous marls and lime- 

 stones, which may, lithologically considered, be united as one series. 

 This series represents, no doubt, the upward continuation of Alpine 

 Muschelkalk much as the Partnach beds do in North Tyrol. ^ Zones 

 may be followed in which certain fossil genera predominate in the 

 number of individuals and species ; but the palaeontological facts 

 give us not so much a clear succession of types as an index to the 

 facial conditions which influenced the life of the period. 



For instance, Halohia Lommeli is a fossil bivalve which is common 

 in tufaceous beds both of Buchenstein and Wengen age ; but in 

 Buchenstein limestones the general character of the fauna is more 

 like that of the Muschelkalk, whereas limestones of the Wengen age 

 contain the remains of Corals and Echinoids like those in the next 

 following Cassian deposits. Again, Posidonomya Wengensis is another 

 bivalve which gradually outnumbers Halohia Lommeli in tufaceous 

 beds belonging to upper horizons of Wengen beds, and it is a fossil 

 which again and again reappears in Cassian time always associated 

 with the same lithological character of deposit, and shewing but 

 slight varietal changes in its outward form. It is one of these 

 persistent types which saw the birth and destruction of innumerable 

 shoals of less fortunate species and genera characteristic of the 

 Cassian limestones. 



In the district of Upper Fassa there are true Augite Porphyry 

 lavas of Lower Wengen age, which appear more or less inter- 

 stratified with grits and tuffs. In the Enneberg districts, i.e. 

 north of Upi^er Fassa, the lavas pass into black earthy tuffs and 

 crumbling grits, in which the fauna is very limited and fragments 



1 " Contributions to the Geology of the Wengen and Cassian Strata in South 

 Tyrol," by M. M. Ogilvie," Quart. Journ. Geol. Soc, vol. xlis. p. 47, February, 1893. 



2 "Ueber die Entwicklung u. Verbreitung der Partnachschichten," etc., by Dr. 

 T. Skuphos, Jahrb. der k.k. Geol. Eeichsanstalt, 1893, Ed. 43, p. 178. 



