~ 
i 
RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 183 
occur are composed of glacial debris. Along the whole northern 
boundary of the area there is an abrupt escarpment, facing northward, 
extending from the island of Odensholm through Baltishport and 
along the southern shore of the Gulf of Finland to the mouth of the 
Narowa, and thence across country south of Petrograd to the Sjass. 
Where this borders the sea it is usually very steep, often perpendicular 
or overhanging. In the Government of Petrograd it is a steep slope, 
but usually without exposures of rock except where cut by streams or 
by the opening of quarries. This cliff, or “Glint,”! is of variable 
height; only fifteen feet on Odensholm, it reaches its maximum height 
of 206 feet at Ontika in the eastern part of Esthonia, and probably 
averages 75 to 100 feet. The strata composing the top of this cliff 
are, remarkably enough, practically always the same, being the rather 
hard magnesian limestone of the lower part of zone C or the “ Echi- 
nosphaerites” layers. Such being the case there are many excellent 
exposures of the part of the Ordovician below this horizon, and, 
where there is not too much talus at the foot of the cliff, the upper 
part of the Lower Cambrian is usually shown. 
From Petrograd eastward, no strata of the Ordovician are exposed 
above the Echinosphaerites beds. The higher strata are to be found 
in the part of the Government of Petrograd west of the metropolis, 
and especially in the Government of Esthonia. These beds are very 
seldom seen in natural sections, being practically always uncovered 
only by the opening of quarries. All the quarries are of comparatively 
‘small extent and very shallow, so that there is never more than one 
formation exposed in any one quarry, and contacts between forma- 
tions above the Kuckers have never been seen. 
Over large areas in Esthonia the strata lie very close to the surface, 
and even very shallow ditches often penetrate the rock. Among such 
ditches the “Graben” on the estate of Baron Toll at Kuckers, near 
Jewe, is famous as the principal locality of the Kuckers formation. 
Many other ditches, often very small ones, were examined during this 
trip and often afforded the only outcrops over considerable areas. 
FoORMATIONAL NAMES. 
The names applied to the formations in this district of Russia bear 
a direct relation to the above described occurrence of outcrops. In 
the classification proposed by Schmidt the important divisions of the 
1 From the Danish Klint, a reminder of the settlement of this country by the Danes in 
the 12th century. 
