52 W. J. Harris : 



beds north of Forest Creek occur. These beds are on the Wattle 

 Gully horizon, and Didymograptus hifidus is found at more than 

 one place along the line. The beds to the east are only Middle 

 Castlemainian, while, further east still, on the east side of Forest 

 Creek, Upper Castlemaine graptolites are found. 



Mr. H. Herman,! in a brief description of the lodes of Castle- 

 maine, gives a section, apparently based on the one just mentioned, 

 and marks on it three zones — viz., Bendigo, Wattle Gully, and 

 Castlemaine. The above criticism applies to this section also. From 

 a palaeontological standpoint botli are in error in showing the cen- 

 tral beds too high in tlie series. 



Besides these papers there are others dealing incidentally with 

 the district. These, and also Dr. Hall's other papers on grapto- 

 lites, will be referred to when necessary. 



111. Charactepistics of Fossiliferous Rocks. 



Graptolites are widely distributed throughout the district and 

 have been found at more than one hundred localities. They occur 

 in slates of every colour. The slates of the Oncnr/raptus zone often 

 bear a distinct resemblance in colour and texture to certain Upper 

 Ordovician rocks, particularly those exposed along the Saltwater 

 River near Digger's Rest, but in the state of our knowledge na 

 importance should be attached to lithological resemblance. With 

 isolated exceptions graptolites in this district are found only in 

 slates or fine mudstones whicli as a rule are less common than 

 sandstones. Limestone of Ordovician age is absent. Quartz grit 

 ridges and bands of coarse sandstone occur, but, thovigh it may be 

 possible to do so, no attempt has so far been made to correlate 

 them. One is therefore compelled to rely entirely on the fine sedi- 

 ments, often so cleaved that the fossils are difficult to break out. 

 This will be the more readily understood when it is realised that 

 the cleavage is rarely parallel to the lamination and often crosses 

 it at an angle of 30 o or more. It is therefore difficult or impossible 

 to obtain a good idea of the facies of some outcrops, though if the 

 beds are Upper Castlemaine Didymorjrajyfjis caduceus may often 

 be recognised along the broken edge of a slab. 



IV. Limitations of Mathematical Stratigraphy. 



It is almost unnecessary to say that no method of working out ther 

 problems of rock folding in an area is more accurate than measure- 



1 Economic Geology and Mineral Resources of Victoria. Bull. 34, p. 24, Geol. Surv. Vie. 



