76 



Overljring the above-mentioned limestones is a thick 

 series of soft, thick-bedded, red sandstones, interbedded with 

 sandy shales, usually red coloured, with dip E. 10° S. at 48°. 

 These beds are intersected by small creeks, which have carved 

 out fair-sized hills on the western side of the main creek w 



In superior position to the last-named red sandstone is a 

 limestone, 5 ft. wide, laminated and contorted and inter- 

 bedded with purple shales, having a dip E. 20° N. at 65°. 

 Then follow, in ascending order, purple and greenish shales 

 with thin bands of limestone, then a series of small ridges 

 showing scarp faces to the north-west, consisting of red sand- 

 stones and flags. A high ridge follows before reaching a 

 valley which separates the latter from, the Grindstone Range, 

 or Little Bunkers, as described above. 



The north-eastern angle of the Grindstone Range was 

 then followed, where the range passes down to soft and decom- 

 posing sandy flags and shales, which cross the Balcoracana 

 Creek on that side: dip E. 20° N. at 50°, changing to a 

 dip E. 



WILKAWILLINA GORGE. 



This gorge occurs in the Mount Billy Creek (or Ten- 

 mile Creek), situated about 6 miles to the southward of the 

 Grindstone Range. A remarkable exposure of the Archaeo- 

 cyathinae limestone occurs at this spot. The limestone is 

 associated with a great range of hills that are about 600 ft. 

 in height: strike N.W. (dip S.E. at 15°). The fossiliferous 

 limestone forms the bed of the creek for about a quarter of 

 a mile in length. Near its upper part the rock is almost 

 one mass of Archaeocyathinae. The matrix, as a whole, is 

 a white crypto-crystalline marble which, throughout the 

 greater thickness of the limestone, only occasionally shows 

 the presence of the fossils; the latter, most likely, having 

 been largely destroyed in the alteration of the rock texture, 

 but near the top the fossils are better preserved. The most 

 striking feature of this outcrop is that the grain of the stone 

 permits its ready fracture, in such a way that the fossil "cups" 

 can be broken out from the matrix so as to show the external 

 form of the organism. This is the only instance that has 

 come under my observation in which this can be done. The 

 matrix in which the Archaeocyathinae are usually included 

 is of an amorphous and refractory character, and is of the 

 same nature within the fossils as in the surrounding matrix, 

 so that the rock fractures uninfluenced by the presence of the 

 organic remains. The only approximate condition for obtaining 

 the objects free from the matrix, naturally, in the normal 

 limestone, is where the organism has undergone silicification, 

 by which the fossil is produced in relief on the weathered 

 surface, as in the case of the Ajax specimens. 



