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oe BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
lie in colonies at various levels, in some places composing the whole 
of the rock and in others only a few or none being present. 
The greater portion of the rock of the formation appears to be com- 
posed of a yellowish white, fine-grained limestone which is only partly 
crystalline; or a coarse-grained, quite crystalline, dolomitic limestone. 
At some levels or localities there is also a little shale. Schmidt 
(Loc. cit., 1882, p. 526) states that in the east dolomites prevail, 
while in the west the lithology is one of coralline limestone. In a 
general way this conclusion appears justified. Also, in the eastern 
limits, either the upper beds of this formation, or the lower beds of the 
succeeding, consist of unfossiliferous sandstone which Schmidt at first 
considered Devonian; but he later learned that the sandstone is 
overlain by the fossiliferous beds of the St. Johannis formation which 
necessitated his referring the former to the Silurian.? 
Addifer, the type-locality, is in the eastern area. The exposures are 
in an old quarry which has recently been reopened. About ten feet 
are shown of which the lower six feet are typical Pentamerus estonus 
limestone. The brachiopods are not uniformly distributed, but occur 
in patches and in these they are extremely abundant. Many are 
silicified, but others show no microscopic trace of silica. Flint nodules 
are very abundant and many are several inches long. The floor of 
the quarry is composed of a coarse-grained, quite crystalline, dolomitic 
limestone. How thick this is, was not learned. The upper four feet 
of the quarry section consist of a whitish yellow, fine-grained, partly 
crystalline limestone, which, except for a few poorly preserved corals, 
appears to be without fossils. It contains a few white flint nodules. 
Near one of the barns about the residence of this estate a ditch has 
recently been constructed, and in it the same sequence as in the quarry 
is shown. 
East of the railroad station, Wochma, about fifteen miles from 
Addifer, are the old quarries of Koksfer, and Arrosaar. They are 
largely grassed over, but a few of the old dumps permit collecting. 
The rock appears to be a coarsely crystalline dolomitic limestone. 
Fossils seem to be rare, consisting chiefly of Halysites, Cyathophyllum, 
Favosites, and Zaphrentis. Pentamerus estonus was not seen. Many 
yellow or brownish yellow flint concretions are present. These strata 
are higher than those of Addifer. 
At Pajus, a few miles east of Addifer is a small exposure of about 
five feet of soft yellow limestone containing no observed fossils, but a 
1Schmidt. Loc. cit., 1881, p. 46. 
