Tlte Heathcotlaii. 165 



associated with fossiliferous quartzites, whicli resemble those of 

 Mount Ida. Both materials were probably derived from the 

 <lenudation of an eastern extension of the rocks exposed at 

 Heathcote. 



South of the Lancefield Gap another outcrop of hypogene trap 

 is recorded on the survey maps. I have been able to examine 

 the rocks of this outcrop owing to the kindness of the Rev. H. 

 Hennell, of Lancefield, who has collected some specimens for me. 



Mr. Hennell's collection nicludes several varities of diabases, 

 and a specimen of banded chert, which nearly resembles that of 

 the Heathcotian series. The lithological characters and strati- 

 graphical position of these rocks both suggest that they are a 

 southern continuation of the Mount William range. 



Near Geelong there are some more outcrops of the Heath- 

 cotian series. The two largest are shown on the Geological 

 Survey Map, No. 24, S.E., and are there coloured as Trap or 

 Hypogene. They were determined by Selwyn as diabases. An 

 unmapped exposure occurs flanking the granodiorites of the Dog 

 Rocks in the Moorabool Valley. As I understand that Mr. E, 

 G. Hogg is undertaking a study of these rocks, I have only 

 examined them as far as is necessary for the course of this paper. 

 In the Moorabool Valley, opposite the Dog Rocks, is an 

 irregularly foliated amphibolite (No. 149); it is mainly composed 

 of needles of green hornblende, associated with zoisite and some 

 material, probably derived from altered grains of felspar. The 

 rock was a basic igneous rock, intensely altered — in part, no 

 doubt, owing to the intrusion of the adjacent granodiorites of 

 the Dog Rocks. 



A second amphibolite (No. 143) of somewhat the same character 

 occurs at George's Hill in the Barwon Valley. It was collected 

 by Messrs. D. J. Mahoney and G. Voss Smith. This rock is less 

 foliated and the remains of the felspars are larger and more 

 angular than in the amphibolites from the Dog Rocks. The 

 rock has been altered and the ferromagnesian constituents now 

 consist of abundant needles and plates of amphibole. This 

 mineral has an extinction of 12 degrees, a i)rismatic angle of 

 about 123 degrees, and its pleochroism ranges from blue or 

 bluish green to pale green and yellowish green. It may therefore 

 be identified as arfvedsonite. 



