RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 223 



stone were found interstratified with the graptoUte 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 tdrnquisti, Megalaspides dalecarlica, Ampyx pater, Agnostus 

 tornquisti , 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 tdrnquisti 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 nericicnsis 

 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 Gastrikliind, and Lamansky (29) described 

 Megalaspides schmidti from a pygidium found in Bj 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 

 tdrnquisti and Trilobites brevifrons are of no value in the discussion. 

 Ampyx pater is similar to Ampyx nasidus 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 gujde 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 developed 



