196 bulletin: museum of comparative zoology. 



Duboiviki formation. C^ (Upper Linsenschicht and lower part of 

 the Echinosphaerites limestone), of Schmidt. 



This formation, like the Kunda limestone is best exposed at the 

 east, where it reaches its best development on the Walchow River at 

 St. Michael Archangel, opposite Dubowiki, just alcove the steamer 

 landing and below the railroad bridge. At this locality the base of 

 the formation is not seen, but fourteen feet of soft calcareous mudstone 

 are exposed, the base twenty-three and one half feet above water level 

 in the river. This outcrop is capped by twelve feet of the harder 

 dolomitic limestone of the Reval formation. Schmidt and Lamansky 

 state that the upper part of Bm (the Kunda formation) is to be seen 

 in the basal parts of the quarries at St. ^Michael Archangel, but I was 

 not able to find it, and so did not see the contact between the two 

 formations here. The upper part of the Kunda is, however, exposed 

 along the river bank about a mile below the steamboat landing and 

 with the prevailing low dip should still be above the water-level at St. 

 Michael Archangel. The thickness of the Dubowiki at this locality 

 is therefore uncertain. It can not be more than thirty-seven feet or 

 less than fourteen feet in thickness, and is probably twenty-five to 

 thirty feet, as Dubowiki fossils, which seemed to be in place, were 

 found within ten feet of the water's edge. 



Schmidt and Lamansky agree that there is no "Linsenschicht" at 

 the boundary between Bm and Ci, at this locality. Following the 

 Dubowiki westward it is present at various sections, but always 

 thinner than at the typical locality. It is well exposed in th« cement 

 quarry and on the railroad south of Asserien, where it is fifteen and 

 one half feet in thickness. It is here a hard compact limestone, 

 unlike the soft marlv beds at Dubowiki; and at this localitv, as well 

 as at Ontika and all the other localities in Esthonia the "Upper 

 Linsenschicht" is present at the base of the formation. This linsen- 

 schicht is not a definite, rather thin band, like the Lower Linsenschicht, 

 but the linsen are smaller, less abimdant, and scattered through a 

 thickness of six or seven feet. Continuing westward, the Dubowiki 

 formation thins out entirely, so that at Reval the upper Linsenschicht 

 is reduced to a thickness of one foot and at Baltishport to ten inches, 

 and it is at the base of the Reval formation instead of the Dubowiki. 

 The Upper Linsenschicht is therefore a tangential formation and 

 represents the invading base of the Wierland group. 



The fauna of the Dubowiki retains some survivors of previous 

 faunas, though very few species are common to this formation and 

 those belov\'. This formation is particularly marked by the intro- 



