GEOLOGY OF TASMANIA. 65 



passing upwards into shales and sandstones of the upper 

 division of the system, with Gangamo'pitru and Cythere 

 tasmanica (Johnston). 



Fossiliferous limestones and mudstones occur at Variety 

 Bay. At Eaglehawk Xeck. the sea beach exposes grits and 

 conglomerates with rectangular joints filled with oxide of 

 iron, forming a natural "■ tesselated pavement " greatly ad- 

 mired by visitors. The jointing is probably due to the 

 vicinity of a concealed body of intrusive diabase. At the 

 Middle Arm of the Tamar, near Beaconsfield, the fossil- 

 iferous limestones repose on Silurian rocks. Dally- old 

 quarry abounds with Eurydesma cordata. Fossiliferous 

 mudstones, with spirifera, productus, terebratula, pachy- 

 domus, eurydesma, occur on the Meander, near Cheshunt. 

 At Mount Cygnet, the succession is — 3. fenestella zone; 2, 

 spirifera zone ; 1, shaly mudstones. The spirifera sand- 

 stones occur all round Lovett and Lymington. 



On the West Coast, the lowest conglomerates of the 

 system are composed of pebbles of schist and quartzite, and 

 rest on ancient schists in the Barn Bluff district. 



The upper division of the system comprises sandstones and 

 shales, which contain the coal of the period, and includes 

 marine mudstones, overlying the coal in the Mersey dis- 

 trict. In the Mersey Basin, notably, near the Great Bend 

 of the river, near Latrobe, beds of variously-coloured clays 

 enclose thin layers of bituminous shale, called Tasmanite. 

 from the abundance of fossil spore cases of the lycopod Tas- 

 tnanites punetatus (Newton), which contains over 25% of 

 resinous matter. The exact relation of these shales to the 

 other beds in the Mersev Basin is not settled. 



The beds of the Mersey coal measures are grits, varie- 

 gated sandstones, marls, and the coal plant remains are the 

 forms characteristic of the Permo-Carboniferous, viz. : — 

 Glossopterisy Gangamopt eris spatulata, G. ohliqya, Noegger- 

 athiopsis media. Mr. Johnston has also recognised a schizo- 

 neiira (rare). The coal of these measures is superior in 

 quality to the coal in the Jurassic measures, but the seams 

 are not of such importance. They are overlaid by marine 

 marls and limestones, sandstones, and conglomerates, with 

 Fenestella pleheia, Spirifera tasmaniensis. Terfhratula sac- 

 culiis, Pleurotomaria morrisiana, Pachydomus, Aviculopec- 

 ten, Cardiomorpha, Pter'ma, &c. These are called the 

 Upper Marine Beds in Tasmania. 



The upper zones of sandstones and shales at Porters Hill, 

 in the South, correspond with the Upper Marine beds of the 

 Mersey. Two hundred feet of the former are exposed along 

 the Derwent, containing Cythere tasmanicu^ (Johnston), 



