Reports and Proceedings — Geological Society of London. 89 



dentary bone with several teeth in place. The impression of the 

 whole of the inner surface and of the anterior half of the outer 

 surface is preserved. The front half of the inner surface of the jaw 

 is like that of Megalosauras, except in size. Many of the teeth are 

 seen in various stages of projection from their sockets, and the points 

 of two successional teeth may also be seen, and thus the mode of 

 succession of the teeth may be clearly understood. The specimen 

 does not admit of exact comparison with Megalosaunis, and it is 

 named as a new species of Zanclodon — a genus in which the author 

 is also inclined to place some forms described under the names of 

 Palceosaurus, Cladyodon, Avalonia, and Picrodon. 



2. "The Torsion-Structure of the Dolomites." By Maria M. 

 Ogilvie, D.Sc. [Mrs. Gordon]. (Communicated by Professor W. W. 

 Watts, M.A., Sec. G.S.) 



The paper opens with a general account of the work of Richthofen, 

 Mojsisovics, Rothpletz, Salomon, Brogger, the author, and others on 

 the Dolomitio area of Southern Tyrol. It then gives the results of 

 a detailed survey recently made by the author of the complicated 

 stratigraphy of the rocks of the Groden Pass, the Buchenstein Vallej'-, 

 and the massives of Sella and Sett Sass ; together with the author's 

 interpretation of these results, and her application of that inter- 

 pretation to the explanation of the Dolomite region in general. The 

 author concludes that overthrusts and faults of all types are far more 

 common in the Dolomites than has hitherto been supposed. The 

 arrangement of these faults is typically a torsion-phenomenon, the 

 result of the superposition of a later upon an earlier strike. This 

 later crust-movement was of Middle Tertiary age, and one with the 

 movement which gave origin to the well-known Judicarian-Asta 

 phenomena. The youngest dykes (and also the granite-masses) are 

 of Middle Tertiary age, while the geographical position of both is 

 the natural effect of the crust-torsion itself This crust-torsion also 

 fully explains the peculiar stratigraphical phenomena in the Dolomite 

 region, such as the present isolation of the mountain-massives of 

 Dolomitic rock. 



The Groden Pass area, first selected for description by the author, 

 is a distorted anticlinal form running approximately N.N.E. and 

 S.S.W., and including all the formations ranging from the Belle- 

 rop/tojt-Limestone, through the Alpine Muschelkalk and Buchenstein 

 Beds, to the top of the Wengen Series. When studied in section, 

 the strata of the Pass are found to be arranged in a complex fold 

 form, showing a central anticlinal with lateral wings, limited on 

 opposite sides by faults and flexures. Strongly marked overthrusting 

 to S.S.E in the northern wing is responded to by return overthrusts 

 to N.N.W. in the southern wing. The strata in the middle limb of the 

 anticlinal wings bend steeply downwards into knee-bend flexui'es. 

 Through these run series of normal and reversed faults, into 

 which has been injected a network of igneous rooks, giving rise to 

 ' shear-and-contact ' breccias, which have previously been grouped 

 as Buchenstein tuff and agglomerates, and referred to the Triassic 

 period. 



