RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 223 
stone were found interstratified with the graptolite shale, it should 
contain some at least of the species found in the strata where limestone 
only was deposited. In Dalecarlia, Holm (62), found a trilobite 
fauna in limestone interstratified with the Lower Didymograptus 
shales. Six species of trilobites were identified, and five of the species, 
Pliomera tirnquisti, Megalaspides dalecarlica, Ampyx pater, Agnostus 
térnquisti, and Trilobites brevifrons were new and are all restricted 
to this one locality. The sixth species, Niobe laeviceps Dalman 
is not a guide fossil, ranging from the Ceratopyge limestone to the 
Asaphus limestone. The pygidium of Pliomera térnquisti is not known 
but the cephalon and thorax show that it is not a true Pliomera 
but a Cyrtometopus allied to the forms found in the Ceratopyge 
limestone. Similar species are, however, found in higher strata. 
Megalaspides is not yet definitely placed outside this occurrence in 
Dalecarlia. Wiman (88), has described Megalaspides nericiensis 
from the Shumardia shale in Nerike, but there is some doubt as to 
whether this Shumardia shale belongs to the Ceratopyge zone or to a 
horizon in the Planilimbata limestone. 
Wiman (89), also reports pygidia of Megalaspides from boulders of 
Planilimbata limestone in Gistriklind, and Lamansky (29) described 
Megalaspides schmidti from a pygidium found in B, at Papowka. Iden- 
tifications based on pygidia alone seem rather unsafe in this genus, the 
pygidium being so Asaphus-like. The genus has not hitherto been 
suspected in the Ceratopyge limestone, but at Hunneburg I found a 
large hypostoma of the “forked” type in the same strata with Euloma 
and Symphysurus, and as no other member of the Asaphinae is known 
at so low a horizon, it of course suggests Megalaspides. Agnostus 
tornquisti and Trilobites brevifrons are of no value in the discussion. 
Ampyzx pater is similar to Ampyx nasutus of the Limbata and Asaphus 
limestones rather than to the species so far described from the Cera- 
topyge limestone. 
The fauna found by Holm in Dalecarlia is then not very useful in 
the correlation of the Lower Didymograptus beds with the Planilim- 
bata limestone. It contains no species restricted to the Planilimbata 
limestone, and the general composition of the fauna is such that, 
lacking a guide fossil of either, it could be referred to the strata either 
above or below it. Over most of Dalecarlia the Planilimbata lime- 
stone is present, but very poor in fossils. In Jemtland, as indicated 
on page 208 there does seem to be some mingling of the species of the 
Lower Didymograptus shales with those of the Planilimbata limestone. 
The Didymograptus shale is absent from Oeland, is best develeped 
