—. 414-442. 
339 
by the occurrence of a pegmatite dyke 8 miles from the granite 
headland. This is genetically related to the Cape Willoughby 
massif, and carries gem tourmalines. With the crystallization 
of the granite and associated dyke rocks, the igneous cycle 
appears to have closed. 
The foregoing data admittedly are insufficient to deter- 
mine the form of the intrusion, yet the writer ventures to place 
(c) composed of magma, either passively squeezed into a 
subterranean or orogenic chamber, or actively forcing apart 
the country rocks. 
The :chonolite type, therefore, covers a wide range of 
intrusions whose form cannot be considered well characterized. 
lt is thought that, for the Willoughby massif, the evidences 
of underground extension, horizontally, and the apparent 
rapid closing of the igneous cycle are not favourable to a 
batholitic nature. 
s 
emphasized by the fact that the late Tertiary fault scarps 
are developed parallel to the strike of the Palaeozoic folding. 
The structure of the Mount Lofty Ranges has been shown 
to consist of a central geological axis of Pre-Cambrian schists 
and intrusive rocks with a north-east-south-west strike, (2) and 
developed, anticlinorially, a series of sediments dipping 
easterly and westerly from this axis. These sediments on 
the western side are only slightly altered, whilst their eastern 
representatives are markedly metamorphosed, being repre- 
sented by quartzites, schists, and marbles. 
. 05 W. Howchin: Trans. Roy. Soc. S. Austr., vol. xxviii., 
1904, pp. 253.280. W. Howchin: Ibid, vol. xxx., 1906, pp. 227- 
NS W. Howchin: Au. Ae, Adv. Boi, 1907, Beck ©, pp. 
