594 Karl A. Grönwall. 



limestone, but, as regards its geological age there exists a difference 

 of opinion to which a brief reference must be made. Waagen 

 divides this formation into three divisions; — the lower, the middle 

 and the upper Productus limestone, and was originally inclined to 

 consider the entire series as Carboniferous, but later on, was led to 

 include only the lower beds in that group, and referred the upper 

 deposits to the Permian. Nötling and Frech refer the whole of 

 the Productus limestone to the Permian, and compare it with the 

 Zechstein of Germany. To this, again, lively opposition was raised 

 by Russian geologists, Tschernyschew especially, who compares the 

 lower Productus limeslone with the Omphalotrochus horizon {Spirifer 

 Marcoai occurring in both these formations), the middle with the 

 Cora and the Schwagerina horizons, and the upper with the Arta 

 stage. In general, however, the Productus limestone is, nowadays, 

 regarded as Permo-Carboniferous (the lower beds), and Permian (the 

 middle and upper Productus limestone), the Carboniferous forms in 

 its brachiopod fauna being explained by the theory that, in the 

 main, the brachiopods suffered but unimportant alterations during 

 the course of time. As an argument for a younger age for those 

 formations which, consequently, it is wished to consider as purely 

 Permian, the occurrence is pointed out of peculiar, new elements 

 in the brachiopod fauna {Richthofenia, Lyttonia, etc.). 



It is probably unnecessary to give any detailed account of the 

 marine Carboniferous deposits in North and South America, but such 

 an examination is all the more necessary, on the other hand, as 

 regards those of the Arctic regions. Nearest to the most northern 

 parts of the great Russian Carboniferous district in the Urals and 

 Timan, we have the Carboniferous of Nova Zembla, partly the Upper 

 Carboniferous marine formations, which have been known a long 

 time, and, partly, newer discoveries (Lee, 1909) of Lower Carboni- 

 ferous Mountain limestone, with Productus gigantens, which, conse- 

 quently, shows that, in this part of the Arctic district, the Carboni- 

 ferous transgression had ah-eady begun during the later part of the 

 Lower Carboniferous period. We ought to pay special attention to 

 the fact that this Lower Carboniferous fauna here occurs in a bitum- 

 inous limestone. 



Further in the north we have marine Carboniferous deposits in 

 Beeren Eiland, and Spitzbergen, and here we encounter the 

 formations that possess the closest analogy to those of North-east 

 Greenland, both from a palæontological and a petrotogical point of 

 view. Thanks to works published of late years by Joh. Gun- 

 nar Andersson, Nathorst, Holtedahl and Wiman, our know- 

 ledge of the Carboniferous deposits of Spitzbergen and Beeren Eiland 



