544 NOTKS ON THE NATIVK FLORA OF NKW SOUTH WALES, VUl., 



The descent into Burragorang occupies some three or four 

 miles, the point reached being near the junction of the Nattai 

 and Wollondilly Rivers. The road down follows a cutting, 

 which, at one point, winds along the face of the cliff. The 

 valley itself is a magnificent example of stream-denudation. 

 Through the mountain, the waters of the Wollondilly and its 

 tributaries have gradually carved a channel from one to two 

 miles wide, with a depth of 1,750 feet; and, in places, have 

 swept away the whole of the sedimentary strata, which con- 

 sist of Hawkesbury Sandstone, Narrabeen Beds, and Permo- 

 Carboniferous Sandstones and Shales, including a coal-seam, 

 leaving majestic, towering cliffs on either side, which outline 

 the course of the gorge. Up this valley the road now passes 

 for some 10 miles in a southerly direction, after which the 

 river is crossed, and a westerly course followed for about a 

 dozen miles up a gradual ascent to the vicinity of The Peaks, 

 now officially known as Yerranderie. 



Over this latter distance the denudation has been enormous 

 (Plate xviii.), nearly the whole of the sedimentary formation 

 having been swept away, thereby exposing a porphyritic or 

 felsitic rock, in which some rich silver deposits occur.* On 

 several of the elevated spots are remnants of Upper Marine 

 formation, as indicated by the fossils, which are plentiful in 

 places, amongst others identified by Mr. W. S. Dun being Spirifer 

 tasmaniensis, Martiniopsis subradiata, and Merismopteria. About 

 a mile bevond Yerranderie, towards the head of the Tonalli River 

 Devonian fossils (Spirife?- disjuncta) were found in 1905 ; and 

 these beds were subsequently traced northerly, towards the 

 Kowmung River, where they are tilted at a very high angle. 

 The Peaks are the remnants of a dissected chain of Permo- 

 Carboniferous cliffs, towards the extreme south-western edge 

 of what is known as the Permo-Carboniferous coal-basin. The 

 highest, or Far Peak, owes its preservation to a small cap of 



* See Mineral Resources of New South Wales, p. 118, by E. F. Pittman, 

 A.R.S.M. 



