RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 221 
occur between the limestone strata of the Orthoceras limestone, the 
species found being Tetragraptus bigsbyi Hall, Didymograptus extensus 
Hall, and Phyllograptus cor Strandmark. 
The fossils of the Lower Didymograptus shales have been described 
by Térnquist (83). These shales are much better developed in south- 
eastern Scania than about Lund. 
The zone of Isograptus gibberulus contains Isograptus gibberulus 
Nich., Didymograptus extensus Hall, D. patulus Hall, and D. mobergi 
Taqst. . 
The zone of Phyllograptus angustifolius has Didymograptus prae- 
nuntius Tqst., Phyllograptus angustifolius Hall, and Tetragraptus 
pendens praesagus Tqst. 
The zone with Didymograptus balticus has a larger fauna, among the 
species being Didymograptus constrictus Hall, D. balticus Tullb., 
Tetragraptus quadribrachiatus Hall, Dichograptus octobrachiatus Hall, 
and Clonograptus subtilis Tqst. 
The lowest zone contains Tetragraptus phyllograptoides Linrs., T. 
approximatus Nich., T. serra (Brong.), Didymograptus undulatus Tqst., 
and D. holmi Tqst. 
The Ceratopyge zone is poorly developed in Scania, but both the 
Ceratopyge limestone and Shumardia shale have been shown to be 
present, with the usual fossils. 
The Dictyonema shales are subdivided into three zones. 
C, zone with Bryograptus kjerulfi and Dictyonema norvegica. 
B, zone with Clonograptus tenellus in four varieties. 
A, zone of Dictyonema flabelliforme in which, interstratified with 
shales, are beds of limestone with Hysterolenus térnquisti and H. 
lericaudus. 
Very little seems to be known of the thicknesses of strata in Scania. 
On seeing the outcrops in the field, one receives the impression that 
*they are very small. Ina boring made at Stabbarp, northeast of Lund, 
the Chasmops beds were encountered between eighty-six and ninety- 
two meters below the surface and shales of the Phyllograptus ct. typus 
zone at a depth of 102 meters, thus indicating a thickness of about ten 
meters for the Lower Dicellograptus shales. 
At Jerrestad in eastern Scania Olin measured a section 425 em. in 
thickness, all in the Trinucleus zone, and most sections which it is 
possible to measure are of this order or of less thickness. 
