Palaeozoic Geology of Victoria. 97 



The only other fossil obtained was a fish scale, from near the 

 Wellington-Dolodrook junction, regarded by Mr. Chapman as 

 probably belonging to the rhizodont genus Strepsodus (23) 



The general nature of the beds, together with the contained fossils, 

 indicate a freshwater or lacustrine origin, and the shape of the 

 basin appears to have been that of a long relatively narrow trough, 

 at least a hundred miles in length, with a general N.N.W. direc- 

 tion. 



The Melaphyrts. — These have been referred to briefly in a former 

 paper (13;, and two analyses by G. Ampt were included. Reference 

 is also made to Howitt's description of the melaphyres of Snowy 

 Bluff, where at least eight distinct flows separated by beds of sand- 

 stone and shale have been recognised, but they are never of any 

 ^reat thickness (7). 



Until last year, no melaphyre had been noted witliin the area 

 under consideration, but one occurrence can now be recorded in 

 Wallaby Gully, towards its head. 



Ihe section forms a small fall in the channel of the creek, show- 

 ing a bed of melaphyre twelve feet thick resting on red shaly 

 mudstones, with a thin band of mudstone on top followed by sand- 

 stone. The flow is distinctly amygdaloidal at the top and bottom 

 with the usual secondary quartz, calcite and epidote. The central 

 portion is a dense fine grained rock. A thin section of this shows 

 under the microscope a distinct flow structure due to the parallel 

 arrangement of the felspar laths. These have a low extinction 

 angle, and appear to be oligoclase; they are ophitically enclosed in 

 •chlorite into which all the augite has passed. Analyses of this rock 

 are not very satisfactory on account of the great amount of altera- 

 tion which has taken place. The one here submitted is from the 

 •central portion. The low aanount of lime and magnesia is probably 

 "due to secondary leaching, foi:< calcite amygdales are common in the 

 upper and lower portion and, thin sections of these parts also' show 

 calcite. 



For comparison the two analyses by Ampt of samples from the 

 basin of the Moroka are repeated. No. 2 was the freshest sample 

 and, therefore, probably the most normal. 



The Melaphyres are clearly subaqueous basic lava flows, and are 

 alwavs found considerably higher in the series than the Wellington 

 Rhyolites. 



