( 695 ) 
stratum about 1 M. above the beach. This petrographical and strati- 
graphical occurrence is, it seems to me, hardly to be referred to the 
age A; the other specimen in the Groningen museum supports my 
observation only to the length of containing marly remains still 
distinetly to be seen. The place where it was found is, however, not 
further indicated. 
Our Groningen fossils have upon the whole but little in common 
with these Gothland pieces; meanwhile this fossil also oceurs in 
Esthonia near Klein-Ruhde in the Estonus-zone. That is why these 
two pieces have been mentioned here though no further data can 
be brought forward to prove their origin from these Eastern Baltic 
regions through want of material for Comparison. 
I. 
Boulders which correspond in age with the Lower Oesel zone in 
the Eastern Balticum, are not rare near Groningen. BONNEMA already 
pointed it out some years ago (31); this short essay, however, has 
more of a palaeontological character, so that I wish to complement 
these communications and enter into further particulars. 
32. Baltica-limestone. 
In an unweathered state rather hard, tough, fine-grained-erystal- 
line limestones of a bright-gray or light-brownish-gray colour. Some 
pieces are almost impalpable; some parts are coloured bluish-gray 
on the inside, so that the rock may originally have had that colour. 
Through weathering the bright-gray tinge passes into light-yellowish- 
gray ; the uneven fractured surfaces then are very often covered with 
sallow-yellowish and brown spots. Crystalline calcite rarely occurs. 
The limestone is rather pure, but a little marly and hardly ever 
slightly dolomitic. Real dolomites are not among them. Stratification 
is imperceptible. The dimensions of the pieces found amount to 25 cm. 
Fossils are not present in great numbers, chiefly Ostracoda, among 
which Leperditia-shells are the most important. Whilst bright-brown 
in the unweathered rock, the valves which sometimes occur frequently 
in a single piece, have become nearly white by weathering. As is 
often the case with the younger Leperditia-limestones, which are to 
be described later on, this limestone is not unfrequently connected 
with Stromatopora-limestone; the fossils to be mentioned below, 
however, never occur in it. Besides these large Ostracoda-remains, 
small Beyrichia- and Primitia-valves are also frequently found but 
