RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 225 
the Orthoceras limestone is thickest, as on Oeland or at Kinnekulle, 
Asaphus expansus, the guide fossil of the “ Expansusschicht”’ is absent; 
and there is found, above the strata containing a fauna which includes 
a part of the species usually found associated with Asaphus expansus, 
a layer with such quantities of the cystid Sphaeronis pomum as to make 
a veritable cystid reef. No such reef is seen where Asaphus expansus 
is present, as in Ostergétland or the Christiania district. Both 
Sphaeronis and Asaphus expansus are reported from Dalecarlia, but, 
according to Térnquist the former species is exceedingly rare, and not 
quite typical, and that district will probably not prove to be an excep- 
tion to the general rule. 
Very little has been done toward working out the details of the 
various sections in the Orthoceras limestone, so that the sections 
at Kinnekulle and Oeland are really the only ones which can be com- 
pared. On Oeland, one finds above the bed with Sphaeronis pomum 
the Upper Asaphus limestone, with numerous undescribed trilobites. 
Moberg states that this zone occurs nowhere else and it certainly is not 
present at Kinnekulle, where a cephalopod fauna is found in the red 
limestone above the Sphaeronis bed. This cephalopod fauna is that 
normally found in the Gigas limestone, and it seems that there is in 
the Oeland section a zone which is lacking at Kinnekulle. Whether 
the absence of Asaphus expansus from the thick sections is explainable 
by the predominance of red sediments, or whether the Expansus beds 
are actually absent is not at present apparent. It should be observed 
that the extra thickness in these great sections is largely accounted 
for by the unusual development of the Planilimbata limestone, though 
of course the added zones above the Gigas limestone have something 
to do with it. 
In Oeland, at Kinnekulle, and in Delarne, one finds considerable 
limestone above the Gigas limestone, which by the Swedish geologists 
is included in the Orthoceras limestone. This limestone contains 
three faunal zones, according to the Swedish geologists, but the faunas 
of the three seem very much alike. The lower zone contains Asaphus 
platyurus and Echinosphaerites aurantium, fossils found in Ci, of 
Russia, and I/laenus chiron is found in Cig of that country, but the 
other guide fossils are mostly species not found in Russia. The pres- 
ence of Didymograptus geminus in the middle zone of the three in 
Oeland is noteworthy, for it serves to complete the parallelization of 
the Scanian and Oeland sections. 
The presence of Ogygiocaris, which seems to have an exceedingly 
narrow vertical range, in the Nemagraptus zone in Jemtland and in the 
