RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 193 
if completed as planned, also furnish a complete section through the 
limestone. This formation is quite thick in the eastern exposure on 
the Walchow but is very poorly exposed, only the basal portion being 
cut by the extensive quarries, and the greater part being seen only at 
places along the river bank just below Dubowiki. 
At the base of the formation one finds the so-called “ Lower Linsen- 
schicht,” a rather soft clayey limestone six to twelve inches in thick- 
ness, full of small flattened grains of about the size, shape, and color 
of small Leperditias, with which Schmidt first confused them. These 
small “lentils” have a concretionary form and have been shown on 
chemical analysis by Kupffer (27), to consist of clay containing iron 
oxides and calcium phosphate. 
The layer containing these linsen does not seem to have been formed 
under abnormal chemical conditions, for it is fossiliferous, often highly 
so, being in fact noted as the best stratum for Pliomera fischeri and 
Lycophoria nucella, and the fossils are of full size and show no abnor- 
malities. It is probable that the “Linsenschicht” really represents a 
basal conglomerate for the Vaginatenkalk, for in places, as at Reval 
and Packerort, there is a real conglomerate which replaces the “ Lower 
Linsenschicht.”’ 
East from Reval this conglomerate was not seen, and west from 
that city there is no “ Lower Linsenschicht,”’ but both the conglomerate 
and the “ Lower Linsenschicht” represent the basal bed of the forma- 
tion. 
The “linsen”’ of the Linsenschicht are almost opaque in the thinnest 
sections which can be obtained of these soft rocks, but show a definite 
concentric structure. 
An analysis of some of them from Ontika by Kupffer is as follows: 
MMM etre re renN yt, sive ttns, Mitt MSF ies te ot) ey Pa 5.93 
enratrre rete” Se tiiOr VEST ee LOO ON eS a 3.95 
FeO; SE EE aE OF ms SRN E CAC ean. Uc ighally Guat fb eure we eh eles 6 69 92 
Mn,03 Pe an eT eee Ge alc Wiiuticet aon seavtee tile te leh e tal aren Swe ca NS ow ets eck 26 
GL eae eee ey wae et tipo EI 1.21 
Sree eee rr eee Ne SS 46 
PA LAL Lom ee ee fe ee oS. 1.99 
I a es ee a ee Obes SE a, 12.42 
Camera cette Fo ORS yk .68 
Merge et ey oo ee eerie. PS IS e, 3.09 
