HORN EXPEDITIOX — GF.XERAL OKOLOny. 39 



Some of t.lie fossils descrihod l)y Mr. R. I'jthoiidLjf, jun., in Iiis papor "On 

 some Australian species of the Family Aivlweoeyatliimi' " came from Kanyka and 

 Bliuman, in the Flinders Range, occurring in siliceous limestones. These fossili- 

 ferous limestones, according to Prof. Tate, "ovei'lie uiK'onforinalily the nietamorphic 

 rocks which occupy the country to the eastward, l)ordering on the New South 

 Wales frontier." 



(c) Extent. 



In journeying north fi'om Oodnadatta a surlden and striking change is 

 observable in the lithological character of the roclcs at the point where these 

 of Pre-Cambrian age succeed the Lower Silui'ian, four or five miles soutli of 

 Alice Springs Telegraph Station. Leaving (juartzites and limestones we at once 

 find ourselves among rocks of a highly metaniorphic chai-.uter, such as gneisses 

 and schists of various kinds. 



The lowest member of the Lower Silurian series is a hard, dense quartzite, 

 which rests inclined at a high angle unconformably on Pre-Cambrian gneiss. This 

 Cjuartzite rises to an altitude of from TiOO to 1000 feet abo\'e the plain, and forms 

 to a grea(. extent the southern slojie and the sunmiit of a very piomincnt ridge. 

 On the northern slope of this ridge the (juartzite forms a steep perpendicular face 

 for about 200 feet down from the summit. The remainder of the slope is formed 

 of the gneiss. 



This pi'ominent ridge, the northern face of which exliil)its tlie junction line 

 between these two great systems of rocks, viz.. Lower Silurian and Pie-Candirian, 

 i.s traceable almost continuously in a nearly east and west dii'ection for many 

 miles, at least as far as Mount Benstead on the east and licit Kange on the west. 

 In a northern diiection tlu? Pre-Cambrian rocks extend to the lUirt Plain, forming 

 rugged mountains with intervening broken country of a rough hilly natur-e. Their 

 further northern extension is concealed by a superticial covering of sand and 

 alluvium of a'olian aiul fluviatile or'igin. 



Tills plateau, known as the Burt Plain, with its covering of com])aiatively 

 recent deposits, ri.ses to an elevation of over 2000 f(H't al>ov{> sea lev(>l. Out of 

 this plateau thei-e rise the Strangways, Reynolds, and Hart Ranges, all probably 

 composed of these ancient rocks. 



The Hart Range, where examined, viz., near Mount Br-assey, and again 

 twenty to thirty miles west of that point, was found to be eritir-ely cornposeil of 

 these rocks. Their easteiri and wester-ri boundaries are not known. Southerly 



