342 Dr. A. P. Young — Structure of the Tarntal Mass. 



So far there exists no tangible evidence of the presence of 

 a Cephalopod fauna in these rocks. 



In the summer of 1907 a plate of limestone bearing an Ammonite 

 was found by me at a height of nearly 2500 metres above sea-level 

 on the surface of a scree-cone which has accumulated under the high 

 hanging valley known as the Lower Tarntal. The fossil and its cast 

 were seen lying within 2 feet of one another near the end of a trail of 

 limestone flakes evidently brought down by recent avalanches from 

 the steep cliff at the lower end of the high valley. Somewhat lower 

 on the slope of the same cone, called 'Issl' by the inhabitants 

 (PI. XVII, Fig. 5), a fragment with a portion of a Belemnite was 

 found, Mr. G. C. Crick, of the British Museum, has kindly under- 

 taken the description of these fossils. These organic remains, like 

 most from the same source, are ill-preserved. It seems nevertheless 

 desirable to keep a record of all such finds for future reference, in the 

 hope that the accumulated material may in the end throw light on the 

 difficult problems here presented. 



It may be well to explain that an erratic origin for these fragments 

 is out of the question. All the material of the scree-cone is represented 

 in the standing rocks on the slopes of the Tarntal above. The move- 

 ment of snow and ice was always in a downward direction. The 

 ravines radiating in all directions are tributary to deep-cut valleys 

 with capacity sufficient to carry off all the ice of this and the 

 neighbouring heights, and the narrow ridges separating the valleys 

 offer no surface along which the ice from the nearer mountain-masses 

 could have been forced up to this level. 



At times of highest glaciation the snow-limit must have stood at 

 a level very much lower than that at which these fragments were 

 found. This limit for the Alps is given at 1400 to 1700 metres; 

 under exceptional circumstances it may have reached 1900 metres.^ 



Near this level were the sources of the masses of ice on which 

 depended the transport of blocks to great distances. Obviously no 

 block could be carried above the snow-limit. During stages of advance 

 or retreat, when the snow-line approached 2500 metres, the glacier- 

 tongues were much shortened and left their loads at short distances 

 from the roots. 



During the summer of 1908 I again searched this and other screes 

 of similar material, but more especially the standing rocks, the bedded 

 limestones of the cliff above mentioned, and other localities. 



The surface of the flake bearing the ammonite is seen to be 

 roughened by minute protuberances, suggesting at first sight an 

 oolitic structure. Many fragments of the same character can be 

 found on the scree-slope of the Issl. 



Microscopic slides were prepared from several of these flakes. In 

 a groundwork of comminuted material are embedded larger fragments 

 of calcite, on which the microscope shdws structures evidently of 

 other than mineral origin. Dr. Bather, of the British Museum, who 

 kindly examined some of these sections, noted in many of the 

 fragments the reticulate structure belonging to Echinoderms. In 



> Penck & Bruckner, Die Alpen im Etszeitalter, about 1908, p. 1143. 



