B. M. S. Watson — The Beaufort Beds, South Africa. 389 



common occurrence of smoothed and striated payements below it all 

 along its northern exposure seems to show that it is the product of 

 a great continental ice-sheet. 



It is my purpose in the present paper to discuss the mode of origin 

 of the Beaufort Beds. These beds, which have long been famous 

 for the wonderful reptilian fauna which they contain, form the greater 

 part of the Karroo and Orange Pree State. 



The whole series has a thickness of roughly 9,000 feet, the great 

 bulk of which is composed of mudstones. These rocks are usually of 

 very fine grain and, as a rule, are not bedded ; they often show banding, 

 a difference of colour and texture, but are very seldom bedded ; that 

 is to say, it is usually impossible to expose aflat level surface of them, 

 for they break into small cubical pieces so as to leave a quite irregular 

 face. They are broken up by sandstones, usually impersistent, and 

 usually also of very fine grain. In the middle of the series, on Great 

 Winterberg, and also, so Dr. Broom informs me, on the Compass 

 Berg, is a much more powerful development of sandstones of a massive 

 kind and generally of coarser grain. 



The colour of the lower beds is usually dark grey or olive, the 

 sandstones being of the same colour on fresh fractures, although they 

 weather brown. The middle of the series, with the thick sandstone 

 mentioned above, is of a lighter tone, the sandstone being yellow 

 and the shales light green or red. The top of the series is almost 

 entirely red in colour, with some green and yellow beds of sandstone 

 and occasional purplish layers. 



Many unusual rock-types occur. In the upper beds the sandstones 

 are almost invariably cornstones ; that is to say, the angular sand- 

 grains are scattered irregularly in an ophitic manner through large 

 calcite crystals, whose cleavage remains quite apparent. The type 

 is exactly similar to that found in the tipper Old Red Sandstone 

 of Forfarshire. 



Another type of cornstone, resembling some of those in the Lower 

 Old Bed of Herefordshire, in which the crystals are not apparent 

 and the included material is very fine mud, if any is present at all, 

 is also common in the upper beds, where it often surrounds bones. 



In certain places masses of mudstone, usually of a purplish colour, 

 are found, which are penetrated by irregular strings of calcite running 

 in the main more or less vertically, but often branching and having 

 the appearance of the roots of a plant. In one case (Donnybrook, 

 Upper Zwoort Kei, District Queenstown) I found in association with 

 such a rock reniform masses of clear crystalline calcite, about 4 cm. 

 in diameter, in a deep red mudstone. 



In the lower beds the mudstones contain immense numbers of 

 nodules of irregular shapes, which are very hard and apparently 

 only slightly calcareous ; they sometimes surround bones, and their 

 intractable nature adds much to the difiiculty of working on South 

 African fossil reptiles. 



Clay-pellet conglomerates are common, particularly in the upper 

 beds, where they often contain small fragments of bone. Pebbles are 

 almost entirely absent ; except for two or three found by Dr. Broom, 

 none are known from this thick and very widely spread system. 



