BY W. N. BENSON. 691 



with the serpentine and gabbro intrusions, and modified by the 

 same dynamic action as these. They are to be sharply separated, 

 therefore, from the entirely distinct dolerites of the Blue Knob 

 group. 



In Dr. Bonney's collection are some specimens indistinguish- 

 able from M.B., 83, described above, which were obtained by Dr. 

 J. M. Bell, from the Serpentine Belt, Narsatas Hill, (Urals 1) 

 Siberia. They have not yet been described, and I am much 

 indebted to Dr. Bonney for permission to mention them here. 



(6,6). There is a small series of acid dykes intruding into the 

 serpentine at several localities. M.B., 316, occurs near the 

 Devonian limestones, 14 miles south of Bingara. It is a purplish- 

 blue in colour, with small, white felspar-phenocrysts. It consists 

 of albite in three forms. The idiomorphic phenocrysts are slightly 

 clouded by decomposition, and twinned on the albite and mane- 

 bach laws. They are sometimes corroded, and show also strain- 

 effects. The ground-mass consists of very finely divided albite 

 in a mosaic, with irregularly shaped patches and lenticles of 

 water-clear, larger crystals. Set all through, are radiating 

 fibrous aggregates of pleochroic pennine, changing from pale 

 purplish-blue to green. There are also numerous, small, irregular 

 fragments of sphene, and some yellow clinochlore. 



M.B., 230, which intrudes into the serpentine, south of Eumur 

 Creek, is a paler rock. It consists of large, strained albite- 

 crystals, with more or less granulated edges, lying in a mosaic of 

 highly strained, interlocking quartz-grains. A very little of the 

 fibrous pennine is also present. In M.B., 21, the granulation 

 has proceeded still further, and the felspars are almost entirely 

 replaced by exceedingly, minutely powdered albite, lying in a 

 mass of larger, recrystallised but strained quartzes. Where still 

 intact, the albite is passing into tiny flakes of mica. The pennine 

 is absent, but small strings of granular diopside(?) occur. There 

 are also a few grains of rutile. This specimen is a hard, white, 

 granular rock, occurring near the limestone and serpentine at 

 Spring Creek, Bingara, in such a way as to seem an alteration- 

 product of the marble produced by the peridotite-intrusion. The 



