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boulders, hitherto unknown in our country, the last two not having 
been met with in any other country as yet. 
Limestone with Strophomena Jentzschi Gag. 
Among the erratics found when the new tram-shed was being 
built, there was i.a. a plate-shaped piece of rock about 2 e.m. in 
thickness and 1 d,m. in length and in breadth, in which occur a 
large number of dorsal valves of a typical Strophomena. Of other 
fossils this boulder appeared to contain only a longitudinal section 
of a Pleurotomaria and a small pygidium of Asaphus raniceps Dalm. 
so that from this it is obvious that it belongs to the Lower Silurian. 
The rock is a fine-grained, rather hard limestone, with scattered 
small rounded quartz-granules. I have not been able to detect 
glauconite. The primitive colour is undistinguishable, as through 
weathering it has changed into a more or less yellowish grey. 
Also some brownish spots still occur. 
In looking up the literature I soon became aware that the very 
same Strophomena has already been described by Gacen of East- 
Prussia, who termed it Strophomena Jentzschi (15 p. 17 44 pl. V 
fig. 26). One of the blocks in which this fossil has been found, 
consists of brownish grey hard limestone with somewhat weathered, 
yellowish spots. It comes from Spittelhof and contains besides 
numerous dorsal valves of the above mentioned fossil, also the rests 
of a large Strophomena and another irrecognizable brachiopod. The 
other specimen comes from Pr. Holland and is composed of coarse- 
crystalline limestone in which only one dorsal valve of Strophomena 
Jentzschi Gag. occurs, beyond corals and rests of crinoids. Their 
petrographical character induced Gage. to refer both erratic blocks 
to the Upper-Silurian series. However, it will appear presently that 
also these boulders, at all events the first-mentioned, have been 
proved to belong to the Lower-Silurian. On the other hand, according 
to ANDERSSON, the other may possibly originate from the Upper-Silurian 
and contain a closely related species. 
Now in order to make assurance double sure, I begged Prof. ANDREE 
of Königsbergen to send me one of GaGet’s original samples for 
comparison. This request was readily complied with. A couple of 
well-preserved valves of Spittelhof were sent me, for which kindness 
I still feel greatly indebted. 
My suspicion came true in every respect. The short description 
of this fossil by GaceL I quote here for the sake of completeness : 
Umriss querverbreitert, Schlossrand gleich der grössten Schalen- 
