270 DE. J. W. GKEGORY ON THE WALDENSIAN [May 1 894, 



the two. The Cessna radiolaria include two genera peculiar to the 

 Palaeozoic, though there are some previously known only in the 

 Mesozoic. Prof. Barrois x has recently announced the discovery of 

 a pre-Cambrian radiolarian fauna ; the members of this, according 

 to M. Cayeux, all belong to the Monosphaeroidea. The Cesana fauna 

 is, however, much more specialized than this, and includes such 

 comparatively advanced forms as Bliopalastrum. The Ordovician 

 fauna described by Dr. Hinde 2 all belongs to the Spumellaria, with 

 the exception of some doubtful species ; and, moreover, of this sub- 

 class only the two orders Beloidea and Sphaeroidea are represented. 

 The Cesana fauna appears of a more recent type than this, and 

 Rust and Parona would even place it in the Mesozoic. It includes 

 six genera of Nassellaria, while the Spumellaria are represented by 

 the Prunoidea and Discoidea, in addition to the Sphseroidea. 



Pew geologists would be likely at present to argue that the mere 

 presence of fossils in a bed is sufficient to disprove its Archaean age ; 

 but the general aspect of the radiolarian fauna is strongly in support 

 of the view of the Palaeozoic, and even of the Upper Palaeozoic, age of 

 the Cesana schists, a view which was so strenuously urged by Lory 

 (though with a slight difference in nomenclature), and has been 

 re-suggested by Kilian from purely stratigraphical considerations. 



We must, therefore, conclude that the Waldensian gneisses are 

 later than beds which are probably Palaeozoic and may possibly be 

 Carboniferous. This gives the maximum age. The statement has 

 been made that pebbles of the ' central gneiss ' occur in the conglo- 

 merates of the Cretaceous ; I am not aware that this has been asserted 

 by any competent petrologist, and as so many different rocks have 

 been included under this name, it is probable that some fragments 

 of the gneissose mica-schists have been mistaken for it. Dr. Gia- 

 notti, however, assures me that pebbles of the gneiss occur in the 

 Miocene at Lauriano, and the accuracy of his identification cannot 

 be questioned, though other geologists have failed to confirm it. 

 Gastaldi also says 3 that specimens of all the rocks of the Alps 

 occur in the Lower Miocene. This settles the latest possible date, 

 at least for the Paradiso. 



The basic igneous rocks which cut through the schists would 

 limit the date more closely, if it could be proved that they are all 

 of one age. The Clavieres serpentine is later than the calc-schists 

 through which it cuts, and is pre-Triassic, as fragments of it occur 

 in the conglomerates at the base of the dolomites ; and this serpen- 

 tine is far more likely to belong to the basic series in the schists 

 than to the Upper Mesozoic basic series of Mont Genevre. None 

 of the pre-Triassic basic rocks cut the gneiss, though they approach 



1 Ch. Bavrois, ' Sur la Presence de Fossiles dans le Terrain azoique de 

 Bretagne,' Comptes Rendus Acad. Sci. vol. cxv. (1892) p. 326. 



2 G. J. Hinde, ' Notes on Radiolaria from the Lower Paheozoic Rocks 

 (Llandeilo-Caradoc) of the South of Scotland,' Ann. Mag. Nat. Hist. ser. 6, 

 vol. vi. (1890) pp. 40-59, pis. iii., iv. 



3 Gastaldi, Mem. descriz. Carta geol. Ital. vol. ii. pt. ii. (1874) p. 59. 



