298 W.G. Fearnsides—Lower Ordovician Rocks of Scandinavia. 
Lower Didymograptus shales: 
(d) Zone of Lsograptus gibberulus (Nich.), with Azygograptus 
suecicus and Didymograptus hirundo ; 
(c) Zone of Phyllograptus densus (Tqt.) =P. angustifolius, 
with Didymograptus prenuntius and many long range 
species ; 
(6) Zone of Didymograptus balticus (Thg.), with D. vacillans, 
D. filiformis, and many other species; 
(a) Zone of Tetragraptus phyllograptoides (Linrs.), with D. undu- 
latulus, D. geometricus, D. constrictus, etc. ; 
the lowest member of which passes down also continuously into the 
Ceratopygekalk. Owing to the interstratification of the Orthocerkalk 
of Sc&ne between the lower and upper Didymograptus shales it is 
probable that the time value of these various zones is somewhat 
unequal. According to Hennig (S 1) it is probable that the limestone 
belongs wholly to the Gibberulus zone, and as it would seem that it 
represents some part of the Limbatenkalk and Lower Asaphuskalk of 
Oland, it must follow that the lower zones a, 6, and ¢ are together 
the equivalent of the Planilimbatenkalk and lowest Limbatenkalk only. 
In Vestergotland we obtain further evidence in the same direction, 
and, further, are able to follow the easterly thinning of the graptolite 
beds most beautifully. At Hunneberg only dark graptolitic shales 
occur beneath the trap, and these to a thickness of about 35 feet 
represent the two lowest zones with Zetragraptus phyllograptoides and 
Didymograptus balticus. At Kinnekulle the shales are greener, but 
here it is found that the 32 feet measured includes the zone with 
Phyllograptus densus as well as the two lower zones. Here too it can 
be seen that the P. densus zone passes up by alternations into the 
glauconitic base of the local Limbatenkalk. At Klefva in Western 
Falbygden only 10 feet of shale overlies the Ceratopygekalk, which is 
here reduced almost to a line, while at Varnhems, Kloster, and 
Skultorp, only a little further east, only some 18 inches of shale is 
seen, and at Skofde and Ekedalen the recognition of graptolite shales 
as partings among the limestone seems to be purely theoretical.- 
In Dalarne the conditions are exactly comparable with fone in 
Vestergotland, but here the replacement of graptolite deposits by 
limestones follows a north to south rather than a west to east direction, 
Skattungbyn being comparable with Kinnekulle, while Rattvik is 
very like Skultorp or Ekedalen. The Orthoceras limestone.of Boda in 
this district is interesting in that, like the Leptenakalk of Rattvik, it 
occurs as the core of a sharp anticline, and has taken on the crystalline 
structures characteristic of the so-called knoll reefs. 
About Kristiania the graptolitic facies is exceedingly well developed 
(10-80 feet) (K 1), and the calcareous facies comes in at an horizon 
-somewhat higher than at any Swedish locality. Unfortunately the 
subdivision of these shales, 36 of Brogger, has not been worked out, 
but their highest bed seems to contain the equivalents of the Didymo- 
graptus bafidus zone of Arenig. Again, the overlying Megalaspiskalk 
(8ea) belongs to the Limbatenkalk, the Expansusskiffer (3¢) bemg 
equivalent to the Oland Asaphuskalk, and the ‘true’ Orthocerkalk 
(sey) to the Gigaskalk of the same district. Higher beds in this 
