174 Proceedings of the Royal Society of Victoria. 



poraneous glacial action may account for some of the features 

 noticeable among the sediments of this system. Not the 

 least striking is the peculiar bluish and olive colour of the great 

 aiiajority of the mudstones. These have an exceedingly strong 

 resemblance to the clay of the typical glacial deposits of Bacchus 

 Marsh, Victoria, and Wynyard, Tasmania. The derivation of 

 their mud from glacial streams discharging into the Jurassic 

 lake is, therefore, not improbable. 



Origin of Included Pebbles in Volcanic Necks. 



The origin of the included pebbles in the necks is of interest. 

 Two probable sources may be suggested : — 



1. From among the Jurassic sediments, dispersed principally 

 through the sandstones. 



2. From a bed of conglomerate in the Jurassic system, or in 

 some system underlying this one. 



In view of the occurrence of the solitary pebV)les among the 

 local Jurassic strata, the former origin seems the more probable. 



With reference to the latter it may be stated that nowhere in 

 the visible Jurassic strata of the district is there any bed of 

 conglomerate having polished pebbles ; neither is there, with the 

 exception of the conglomerates at San Remo, which occur at sea 

 level, and may perhaps be the basal beds of the series, any 

 deposit extensive enough to be called a bed of conglomerate. 

 Besides, these San Remo conglomerates are composed of rocks 

 entirely different from those under consideration, and the pebbles 

 are not polished. The probability of the derivation of these 

 pebbles, therefore, from a Jurassic bed of conglomerate is remote. 



Then, as regards their possible derivation from a subjacent 

 conglomerate of pre-Jurassic age, there does not appear to be any 

 evidence in support. On the other hand, the absence of fragments 

 of unpolished rocks, except those of Jurassic sti'ata, practically 

 prove that such was not their origin, since it is hardly likely that 

 fragments of the rocks of other beds of the series would not have 

 been included among the volcanic n)aterial had the pebbles been 

 derived from such a source. 



The pebbles in the necks have the same general shape as those 

 among the Jurassics, and are broken in a similar way. They have 



