62 Transactions of the South African Philosophical Society. 



No fossils have been found in their immediate vicinity ; but not far 

 to the north-east of Portugal's River large bones belonging to 

 Titanosuchus occur, and this is a genus which is found in the 

 Pareiasaurus beds in the Gouph. To the west, in sandstones which 

 have been followed round from the Eoggeveld escarpment to the 

 Komsberg, and which pass under the village of Sutherland, there 

 are plants belonging to the genera Glossopteris and Schizoneura. 



The Sutherland Commonage Group. 



A few hundred yards west of the village there is a low escarpment 

 of sandstones ; from the edge of the escarpment the ground rises 

 gradually to the steep dolerite-crowned hills of Yyf Fontein. It is 

 ■on this sloping terrace that the vents we have now to describe are 

 situated. The accompanying plan (Fig. 1) shows their distribution. 



Vent No. I. is a roughly triangular area, well defined on the south- 

 west, but covered with soil on the other sides. Two shafts for 

 prospecting purposes have been sunk in this area, but they are now 

 in great part filled up by fallen material. They are both in a soft, 

 light bluish-grey tuff or weathered igneous rock, probably the 

 former. The deeper shaft was sunk to a depth of 80 feet * without 

 striking the unweathered rock. Near the south-western wall the 

 tuff becomes a sandy breccia, and contains numerous angular frag 

 ments of sandstone and shale. Under the microscope the rock is 

 found to consist of grains of quartz, flakes of brown mica, broken 

 crystals of olivine augite and brown hornblende, and minute grains 

 and crystals of iron ores and perofskite, set in a dusty matrix con- 

 taining much calcite. In other parts of the vent there are outcrops 

 of a grey rock with a compact-looking base crowded with crystals of 

 olivine and pieces of ilmenite up to an inch in length. Many 

 hardened fragments of shale are seen, and there are also flecks and 

 small cracks filled with a mixture of calcite and zeolites. The 

 specific gravity of a fresh specimen without large pieces of ilmenite 

 is 3*11. Under the microscope the matrix is seen to consist of a 

 matted aggregate of fibres with low double refraction which is 

 attacked by dilute hydrochloric acid with separation of silica; in this 

 matrix are magnetite or ilmenite grains, crystals of perofskite, 

 apatite, melilite, grains of augite and olivine, though the augite is 

 not abundant, and numerous flakes of a very pale biotite. The 

 melilite occurs in colourless lath-shaped sections showing the 



* For this and much other information about the prospecting operations in the 

 .Sutherland Division we are indebted to Mr. J. Kennedy, of Sutherland. 



