Dr. A. P. Younrj — Strucfure of the Tarntal Mass. 343 



one instance a section of an Echinoid radiole of Diademoid type 

 could be recognized. This form is probably not older than Upper 

 Trias ; the slide on which it occurs was taken from the flake of 

 limestone bearing the Ammonite. 



Markings, similar to those above described, are to be seen in 

 microscope sections from the standing rock of the cliffs above the 

 Issl. These observations are in keeping with the conclusion already 

 arrived at as to the source of the fossil. 



The breccias of the Tarntal band (No. 4 of section, p. 340) 

 have characters which distinguish them from the breccias which 

 form a small part of the little disturbed mass of Triassic dolomite 

 below (No. 1 of the section). The latter contain little or no quartz ; 

 the fragments and matrix are similar in character and are with 

 difficulty distinguished. In the Tarntal band the fragments vary 

 in character, and on weathered surfaces show up well against the 

 matrix ; some of the fragments show the original bedding planes. 

 On the Mieselkopf ridge angular flakes of a phyllite nearly a foot 

 in length have been seen among the inclusions in a similar rock. 

 In the Upper Tarntal was found a small block of the breccia which 

 contained numerous inclusions of green talc, a mineral not infrequent 

 in the schists near the serpentine contact. 



The question arises — Is the brecciation of the Tarntal dolomite 

 an oecogenous or an apoecous character, i.e. has it been acquired 

 before the rock left its original site or during the movement of 

 translation ? Reasons will be given for the view that both brecciation 

 and veining with quartz are cecogenous. 



An assemblage of rocks similar to that of the Tarntal mass is seen 

 at the Mieselkopf ridge, at a height of 2560 metres, some 

 9 kilometres west of the Tarntal. There is the same massive 

 unstratified dolomite several hundred metres in depth, showing no 

 effects of shearing or crushing, surmounted by a band of highly 

 contorted rocks. Here the dolomite breccia, the schists, and the flaggy 

 limestones form several distinct layers which stand at a high angle 

 of dip (PL XVIII, Fig. 8, and see Map, p. 341). 



The nearer view of the Mieselkopf ridge from the east conveys 

 the suggestion of a sharp synclinal fold (PL XVIII, Eig. 8). 



In the vicinity the talc-bearing schists are well developed, and at 

 2460 metres, some 200 metres below the crest, is a mottled red and 

 green calcareous rock without foliation, much like that seen in 

 company with ophicalcite at the serpentine contact, in the quarrj' at 

 Pfons, near Matrei, some 14 kilometres to west of Tarnthal. At the 

 site under the Mieselkopf the rock forms the core of a band of schist in 

 the strike of one of the -vertical layers of schist on the ridge. Some 

 50 metres higher and in the same strike is an occurrence which may 

 throw some light on the relations between dolomite breccia and schist. 

 Within a space of about 3 feet are some eight or ten vertical plates of 

 dolomite breccia alternating with as many bands of the schist, which 

 is foliated in a vertical plane parallel with the plates. Fine quartz 

 veins traverse the dolomite in all directions, invariably stopping short 

 of the schist which is free from veins. The phenomenon cannot be 

 explained as a stratigraphical sequence. The dolomite breccia, 



