470 Notices of Memoirs — Prof. Bonney — Alpine Oeology. 



causing a strait or gulf, dividing the Land's End from the maim 

 eastern portion of the county. 



In this shallow strait the clays and sands were deposited, and just 

 such an assemblage of mollusca is found as will bear out this view.. 

 Scarcely any of the shells which are of living species are known to 

 inhabit such deep water as Mr. Eeid indicates, while the majority 

 show the presence of a laminarian zone, extending to not more than^ 

 fifteen fathoms. This bathymetrical range is the chosen habitat of 

 the Bissoce, who are all vegetable feeders, and of the Nassce, which. 

 are predatory and always plentiful just below low-water mark ; 

 and what appears still more conclusive is the number of Hydrobifii, 

 which have a close connection with Littorina and indicate shallow 

 depth and close proximity to shore. 



It is hoped that a more detailed examination of the mullusca fauna 

 may soon be completed, and the whole series added to the National 

 Collection. 



III. — Preliminaey Note on Traverses of the Western and of 

 THE Eastern Alps made during the Summer of 1887. By 

 Prof. T. G. Bonnet, D.Sc, LL.D., P.E.S., F.G.S. 



THE first traverse was made along the line of the Eomanche from 

 near Grenoble to the Col du Lautaret, and thence by Briangon 

 over the Mont Genevre and the Col de Sestrieres to Pinerolo at the 

 edge of the Italian plain. The second went from Lienz, across the 

 central range of the Tyrol to Kitzbiihel, and the rocks of this range 

 were also investigated at other places, During both traverses the 

 author had the advantage of the assistance of the Eev. E. Hill, who 

 had accompanied him on a similar journey in 1885. 



The results of their examination fully confirm the views already 

 expressed by the author as to the nature and succession of the 

 crystalline rocks of the Alps. 



(1.) The lowest group consists partly of modified igneous rocks 

 (which indeed occur at all horizons), partly of gneisses of a very 

 ancient ( Lauren tian) aspect. 



(2.) The next group, up to which there seems a gradual passage, 

 consists mainly of more friable gneisses and moderately coarse 

 mica-schists (Lepontine type). This group is commonly less fully 

 developed in the above districts than in the Central Alps, having 

 probably been removed by very ancient denudation. 



(3.) The third group has an enormous development. It forms 

 a large part of the Cottian and Graian Alps, and it flanks the central 

 axis of the Eastern Alps on both sides, often passing beneath the- 

 ranges of Secondary strata, which here form the northern and 

 southern ranges. It has been traced almost without interruption 

 from east to west for more than fifty miles on the southern, and 

 eighty on the northern side of the central range. It has a very 

 close resemblance in all respects to the uppermost group of schists 

 in the Central Alps, found to some extent in the Lepontine and yet 

 more largely in the Pennine Alps, and the author fully agrees with 

 the Swiss and Austrian ffeologists in regarding it as in the main 



