BY W. N. BENSON. 587 



ten, Martiniopsis, and obscure casts resembling Astartila, Edmon- 

 dia, Mourlonia and Ptycomphalina. It is impossible to fix the 

 horizon of these, but they are more probably of Upper than 

 Lower Marine Age, with portion of the upper freshwater measures. 



The rocks do not make any good outcrop, and accordingly the 

 boundaries drawn, rest entirely upon the change of surface-slope. 

 At Reichel's, the fossils were found in the low saddle between two 

 hills of Bowling Alley rocks, but the wide opening of the river- 

 valley at this point, both on the eastern and the western side, is a 

 marked and unique feature, which may be due to the differential 

 erosion of the soft shales and sandstone from among the harder 

 Devonian rocks. In that case, it is probable that Permo-Carboni- 

 ferous rocks lie beneath most of the widespread alluvial covering 

 of the valley-floor. 



The rocks are doubtless portions of a great overspreading sheet 

 of Permo-Carboniferous rocks, and were preserved by down-fault- 

 ing probably during the early Mesozoic period of tectonic move- 

 ment. As they lie more than 40 miles from the nearest known 

 masses of Permo-Carboniferous rock, it will be seen how great an 

 extension of the area of Permo-Carboniferous sedimentation is 

 indicated .by them. 



(8) Tertiary Gravels and Clays. — These lie beneath the basalt- 

 masses, and are most easily described with a locality-grouping. 



The Yerrowinn Gravels are exposed on the south side of Dun- 

 can's Creek, where they are about 120 feet thick. They are here 

 composed of coarse gravel. On Folly Creek, to the west, they are 

 much thinner, about 20 feet in all, and may be traced thence on to 

 the watershed between Munro's and Folly Creeks. Here they are 

 also gravels, but finer sandy bands have been found with leaf- 

 impressions. Some beautifully preserved, coniferous wood occurs 

 in these gravels, similar to that found near Barraba. The slope is 

 to the west, with a fall of 210 feet in 2J miles. The boulders 

 consist of reef quartz- jasper, with granite and phyllite. 



In the basalt, about 200 feet above the top of this gravel, there 

 is a small, narrow band of gravel at the eastern face, and a third 

 horizon is suspected still higher up. Near the head of Duncan's 



