E. J. Dunn — The Transvaal Ooldfields. 171 



10. Species 6 (apparently allied to Cobus). 



The hinder portion of a cranium (B. M. No. 39559) indicates a 

 smaller animal than the last, agreeing very closely in general 

 characters with the African genus Cobus, but perhaps too imperfect 

 for generic determination. 



11. Species c {Antilope patulicornis, nobis). 

 Vide Pal. Ind. ser. 10, vol. i. pi. xxv. fig. 3. 



The hinder part of a cranium (B. M. No. 39559a) agi'ees with the 

 type frontlets of this form, and apparently indicates a species allied 

 to the two preceding ones ; but with more divergent horn-cores. 



12. Species d (of uncertain affinity). 

 The hinder portion of a cranium in the British Museum (No. 

 39559&) belongs to a species distinct fi'om any of the foregoing, of 

 which the affinities are by no means clear. It closely resembles 

 an imperfect cranium from the Lower Pliocene of Pikermi figured 

 by Gaudry in the 'Animaux Fossiles et Geologie de I'Attique,' 

 pi. lii. fig. 1. 



VI. — On the Mode of Occurrence of Gold in the Transvaal 



GOLDFIELD. 

 By E. J. Dunn, Esq. 



IYENTUEE to submit the subjoined account of the mode of occur- 

 rence of gold in certain localities in the Transvaal Gold-field, in 

 the hope that it may prove of interest to some of your readers. 



At the " Waterfall " Diggings thin leaders, ranging from half an 

 inch to eight or nine inches, and having a dip of about 50°, cut 

 through nearly horizontal strata of shales, soft sandstones, decom- 

 posed calcareous beds, etc. The leaders consist of siderite and quartz, 

 the siderite fi'equently preponderating. Sections of these leaders 

 show sometimes walls of siderite, with quartz in the centre ; and in 

 other cases the walls are of quartz, with siderite in the centre. The 

 proper walls of the vein are frequently mineralized back several 

 inches from the junction with the " country." Where so mineralized, 

 cubes of iron-pyrites in an oxidized condition are abundant, and gold 

 also occurs. 



The interesting point in connexion with these auriferous leaders 

 is that the gold is almost invariably associated with the siderite. I 

 did not observe a single instance in which the quartz was penetrated 

 by gold ; whereas the siderite is frequently thickly studded with 

 gold in the form of small plates, in arborescent forms, and in minute 

 particles. The siderite is altered, but still preserves its distinct 

 cleavage. It is dark-brown in colour, and in places is stained black 

 by manganese oxide. The quartz is translucent, and bears the 

 impi-ess of the rbombohedrons of siderite. 



Associated with gold in these veins are native bismuth, carbonate 

 of bismuth, yellow sulphuret of copper, muriate of copper, oxide of 

 copper, and hematite. There are a great many of these leaders, and 

 nearly all are aui-iferous, and most are richly so. 



"Woodward's leaders," at Spitzkop, cut through similar rocks; 

 but, though siderite is present, it is less abundant ; the veins here 



