TJie Older Tcrtiaries of Jllaitdc, etc. 183 



as in the lower portion, and are often associated with small 

 quartz pebbles. In a section displayed on the roadside between 

 the State School and the old mill, at The Clyde, we measured one 

 embedded basalt block exposed, and found it ten feet long 

 and four feet thick. Another boulder was five feet by three 

 feet six inches ; and these great masses were associated with 

 numerous fragments of all sizes, down to small pebbles ; and all 

 wt'i'e well rounded. Packed in between the boulders was a 

 deposit of conuninuted polyzoa, broken and worn spines of 

 echini, fragments of l^rachiopod shells and of pectens, but per- 

 fect specimens of any kind were rare. 



It may be that the officers of the survey felt the necessity of 

 accounting for the alteration of the rock to a crystalline lime- 

 stone by igneous action, and were led to attribute it to an 

 intercalated flow, taknig the large included blocks as portions of 

 such a sheet. The subsequently opened sections, liowever, 

 dispose entirely of such an interpretaticni. On the opposite side 

 of the river from this Clyde section, a large quarry is a con- 

 spicuous object on the hillside. This shows a clean face of nearly 

 thirty feet, and is about fifty yards in length. The limestone, 

 which foi'ms the greater part of the quarry floor, rests on a very 

 uneven l)asaltic surface, and extends about ten feet up the face. 

 It is distinctly less altered as we go up from the volcanic rock, 

 an I is capped Ijy arenaceous and calcareous beds, which reach 

 apparently to the top of the hill. The cause of the change in 

 character has, then, evidently acted from below, and is not due 

 to a more recent flow of basalt. What this cause may have been 

 is not clear to us, but we have recorded a similar alteration in 

 the polyzoal rock overlying the ash beds of Curlewis.* Mr. D. 

 Avery, M.Sc, has kindly examined the rock for us, and says 

 there is only a very small amount of magnesia present, so 

 that the changed character has not been brought about by 

 dolomitisation. 



Wherever the limestone is unaltered it is seen to be, both 

 lithologically and paheontologically, the equivalent of that of 

 Waurn Ponds. 



* Proc. Roy. Soc. Vic, 1893, p. 3. 



