50 Miss M. M. Ogihie— Coral in the " Dolomites." 



particular mode of transition from conditions of deposition favour- 

 able for the Cassian fauna to those in which the Kaibl fauna was 

 enabled to make an occasional appearance in the South Tyrol 

 dolomites. At a very little distance above the base of Schlern 

 dolomite all signs of Coral life disappear, and the deposit looks a 

 homogeneous rock, although always retaining local variation in the 

 degree of its dolomitism. At this stage the rock often shows typical 

 Oolite structure. As regards the presence or want of stratification, 

 it has as little to do with the question of the Coral Reef origin 

 of the dolomite as the amount of magnesic salts in the rock — 

 stratification is present and absent in one and the same " Eeef." 



In the highest horizons of Schlern dolomite there is infinite 

 irregularity in the relations of fossiliferous and unfossiliferous beds ; 

 these horizons have been proved palgeontologically to belong to the 

 Eaibl period. In them Corals and Echinodenns reappear again in 

 some abundance in the Groden and Enneberg districts. Dolomitic 

 shales may be regarded as the typical sediment, giving place locally 

 to sandstones and limestones, in which strand-faunas and plant- 

 remains are imbedded. In one or two places Corals formed thin 

 reef-like extensions over preceding plains of algal and marine 

 origia. The fauna everywhere has many reminiscences of the 

 Cassian fauna, but has marked local as well as zonal characters. 

 Thanks to the occurrence of a few leading Molluscan types of wider 

 distribution in Eaibl strata, one or two horizons of time are cleai'ly 

 identifiable in the succession. Life was often made impossible, and 

 brightly-coloured magnesian marls silted up large basins. Dolomitic 

 mud and rauchwackes accumulated, or beds of dolomite or g3'psum 

 were separated from the water in inland seas and lagoons of what 

 seems to have been a South Tyrol "Eaibl" Archipelago. The best 

 example of the heteropism in Eaibl times is afforded by Schlern 

 Mountain, where the stratigraphical relations of the fossiliferous 

 well-known "Schlern plateau" Eaibl beds have been carefully 

 worked out by von Wohrmann.' He says: "At one place we have 

 a fauna exceptionally rich in individuals, in others we find the same 

 horizon represented by a Coral bank, or by ferruginous marls wholly 

 unfossiliferous, etc. These contrasts cannot be explained merely by 

 the irregularity of the sea-floor, which is readily recognizable through 

 the rapid increase or diminution in thickness of the strata ; we are 

 bound to accept current action in addition, making the relations 

 locally so favourable that a numerous assemblage of Bivalves, 

 Gasteropods, and other organisms were able to thrive within 

 narrow spacial limits (for instance, the immediate neighbourhood 

 of 'Schlern-klamm') without spreading into the surrounding area" 

 {loc. cit. p. 219). I have had experience of very similar facts at 

 Sella, Sett Sass, and Lagazuoi. On Sella, as at Schlern, a Coral- 

 bearing dolomite of no great thickness appears amid the dolomitic 

 shales on the plateau. Again, on visiting the top of Lagazuoi, I 

 found unfossiliferous beds of a hard dolomitic sandstone, perfectly 



1 Von "Wohrmaiiii, u. Koken. "Die Fauna der Eaibler Scliichten vom Sclilem 

 Plateau." Zeitschrift d. D. Geol. Ges. 1892. 



