The Heathcotian. 153 



occurrence of pebbles of the metamorphic rocks in the breccias 

 on the summit of Mount Ida. (No. 8'). 



The Silurian rocks can be seen in close contact with the 

 diabases on the eastern side of the Murray-road, opposite the 

 so-called copper mine. There is no sign of any contact altera- 

 tion of the Silurian rocks there. The silurian sandstones are 

 often I'eddish-brown, owing to the abundance of material, which 

 the microscope shows to be mainly decomposed diabase. 



The junction of the silurian rocks with the diabase series is 

 rarely shown, as they are generally separated by the alluvium 

 along the Mclvor Creek ; but in some workings by the old 

 scheelite mine at South Heathcote the silurian rocks were 

 exposed close to the diabases ; there is no apparent sign of 

 contact alteration in the silurians ; the development of the 

 scheelite was probably a secondary change due to the action of 

 solutions. 



III. {B). — The Ordovician. 



The ordovician rocks to the south and west of Heathcote are 

 in the main sandstones, quartzites, shales, micaceous mudstones 

 and shales. The strike is generally from north to south ; but 

 near Heathcote it changes to from N. 30 W. to S. 30 E. The 

 beds, as a rule, are not much contorted, and the bedding is fairly 

 regular. Some of the beds which had been mapped as ordovician 

 slates, Mr. Howitt has determined as phyllitic schists. Most of 

 the oi'dovician rocks still clearly show their clastic origin, and they 

 have not been converted into schists. The rocks are themselves 

 unfossiliferous, except for a band which lies along the eastern 

 border of the ordovician series, in the parish of Knowsley East. 

 The fossiliferous band occurs across the paddocks from 3q, 3p, 

 3m, 3], 3n, 31, and 3i. It has been carefully described by Mr. 

 Lidgey and Mr. Ferguson, and the latter has twice collected 

 from it a series of fossils. The first determined fossil from this 

 band was described by Mr. R. Etheridge, jun., as a new genus 

 of trilobite, of cambrian age. He named it Dinesus ida. 



1 The reference numbers are to the bibliography on p. 151. 



