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AUG. F. FOERSTE 
about two thirds of the distance from Norway to Spitzbergen. ' 
Here A. G. Nathorst collected in 1898 the bulk of the fossils 
studied by Holtedahl. This was supplemented by material col- 
lected in 1899 by J. G. Anderson, which, however, did not con- 
tain much that was new. Both collections are deposited in the 
Riksmuseet, at Stockholm, Sweden. These collections consist 
of Black River fossils occurring in the upper part of the Heclahook 
system in a series of strata known locally as the Tetradium 
limestone. From this Tetradium limestone the following species 
were listed: Tetradium cf. syringoporoides Ulrich, Bryozoa several 
species, Crinoid stems, Rafinesquina sp., Orthoceras (Kionoceras) 
sp. (Holtedahl, Plates XI, fig. 2), Endoceras (Vaginoceras) sp. 
(Holtedahl, Plates X, fig. 1), Endoceras (Cyclendoceras) sp. 
(Holtedahl, Plate IX, fig. 5), and Gonioceras {occidentale Hall?) 
sp. (Holtedahl Plate XI, fig. 3) ; also various Actinoceroids 
(Holtedahl, Plate X, figs. 2, 3, and Plate XI, fig. 1). 
Regarding these species Dr. Holtedahl emphasizes the fact 
that Tetradium and Gonioceras are typical American genera, 
well represented in North America, while in Europe Tetradium 
is listed only from the Borkholm in the Baltic area and Gonioceras 
apparently does not occur at all. In Asia, moreover, Gonioceras 
is known only at a single locality, in West Shantung in North 
China, where it occurs associated with Actinoceras all. tenuifilum 
Hall, another typical American Black River species. Regarding 
Actinoceras, Dr. Holtedahl states that this genus may be said 
to be characteristic of the American faunal province in Ordovician 
times, while in Silurian times it has spread also to Europe and 
is found quite commonly in England and in the Scandinavian- 
Baltic regions. A true Actinoceras, somewhat resembling the 
Silurian Actinoceras imhricatum Hisinger, is quite common in 
the uppermost Ordovician of some districts at the western side 
of the Kristiania region, in Hadeland and Ringerike. This 
~ Norwegian occurrence possibly may indicate that the Actinoceras 
stock came from the west or northwest in upper Ordovician times 
and spread in Silurian times all over southern Norway and 
Sweden. 
