Fish origins— fresh or salt water? 275 



indicates that the fishes are not associated with the marine invcrtcbraics. The tigiires 

 given are depths from the surface, in metres: 



to 270-70 Typical Old Red sandstone (Gedinnian) with osiracoderms 



270-70 to 295-80 Sandstones more drab than those above, micaceous, 



somewhat calcareous; Cyathaspis harroisi at 278-281; no other 



fossils reported 

 295-80 to 296-30 Dark blue schistoid sandstone with marine shells 

 296-30 to 298 Pale grey sandstone with Pteraspis i^osseleii 

 298 to 318-20 Dark blue schistoid sandstone with marine shells 

 318-20 to 331-70 Pale grey sandstone with Pteraspis gosseleti; a bonebcd 



at base 

 331-70 to 350 Dark blue schistoid sandstone with marine shells 

 350 to 473 Marine beds of Ludlow age, with Dayia navicula, etc. 



The section here is clearly comparable in its general nature to a typical English 

 section — first marine Ludlow beds; then " Passage beds " in which final marine 

 phases alternate with non-marine ostracoderm layers, including an initial bonebed; 

 these are followed in turn by a typical Old Red sandstone of continental type. 



6. Scania 



The remaining European vertebrate localities are from the Baltic region. There 

 are here excellent Silurian sections in the main typically marine in nature. As was 

 true both to the north and west in Great Britain and Norway, and to the south in 

 Podolia, we are in a region in which there was a change from marine to continental 

 deposits at about the end of Silurian times. But although it is probable that typical 

 " Old Red " deposits were formed in this area, none is preserved, and in consequence 

 we are left to interpret the story from decapitated Silurian stratigraphic columns from 

 which the terminal Old Red has been secondarily removed. Although the island of 

 Gotland is the classic locality for study of the Baltic Silurian we shall use that of 

 adjacent Scania instead, since but a single vertebrate specimen (not mentioned by 

 Gross) has been found in Gotland, whereas Lehman (1937) has described numerous 

 scales, spines and other fragments from Scania. 



In Scania we find a Silurian sequence comparable in nature to those we have 

 described in other regions. For most of its vertical extent the Silurian is purely 

 marine in nature, including Rastrites, Cyrtograptus and colonus stages covering the 

 Valentian and Salopian. The last is succeeded by the Oved-Rams^sa stage, generally 

 equated with the Downtonian. As Born notes (1926, 160), this stage contains few 

 invertebrates. " Es handelt sich hier um eine typische verarmte Fauna der Ober- 

 gangsschichten, die zum kontinentaler Old Red uberleitet." The Oved-Ramsasa is 

 composed mainly of coarse elastics. Limestone is found only in the lowest of four 

 zones; it is followed by barren white and yellow sandstones; then by grey-blue clays 

 containing fishes and eurypterids and also a variety of invertebrates; fuially by red 

 sandstones containing nothing but Lingula and ostracods. The Oved-Ramsdsa is. 

 thus, ecologically a Downtonian type of deposit. It is certainly no more marine in 

 nature than an estuarine-deltaic situation, and even so. the fragmentary nature o\' the 

 fish remains strongly indicates an upstream origin, with the remains, as Liuman 



