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carboniferous glacial beds, and to be overlain unconformably 

 by the Miocene sandy limestone. 



It is in one of the uppermost yellowish sandy horizons of 

 the glacial beds that the barytes sand crystals occur. The 

 particular bed is only a few inches in thickness, and weathers 

 into soft, friable sand-rock, with hard nodular barytes aggre- 

 gates distributed plentifully throughout. 



Specimens were collected from the associated beds, and 

 tested for sulphate. Contrary to expectation, none was found 

 present, though other characters of the beds are evidence of 

 their epirogenic formation under arid conditions ; possibly 

 gypsum was present formerly and has since been removed. 



Several of the sandy beds were found to be firmly cement- 

 ed by a calcite cement in optical continuity, and represent, 

 therefore, a massive form of Foutainehhau Sanchtone. 



The typical form of the ''barytes sand crystals" is in 

 bunched aggregates averaging 3 cms. diameter. Various 

 intermediate stages are well represented. Sharp crystal edges 

 are never developed, even on specimens collected iii situ. 

 Single individuals are flat, tabular forms, with edges rounded. 

 Divergent groups of three or four individuals, having the b 

 axis in common, are most usual (c.f. pi. xxi. fig. 3.) In cases 

 where a large number have thus grown together, especially 

 when, as in more complicated groups, cross-growths enter into 

 the aggregate, the fully-developed form, with surface re- 

 sembling peach-stone corrugations, is produced (c.f. pi. xxi. 

 fig. 4). 



II. Radial-Nodular Barytes. 



Specimens of an unusual form of Barytes collected in the 

 Brighton Lower-Cambrian limestone quarries were, several 

 years ago, presented to the University by Professor E. H. 

 Rennie. 



The barytes nodules are as much as 12 cms. in diameter, 

 with a somewhat irregular smooth exterior, occasionally 

 marked by growth lines; interiorly, a radial arrangement is 

 evidenced. The mineral is dark-brown in colour, transparent, 

 and has a vitreous lustre; hardness, about 3*2; fracture, con- 

 choidal. 



Some of the specimens pass outwards into a yellowish- 

 white opaque radial curvilaminar form, with silky lustre. A 

 qualitative analysis showed the mineral to be nearly pure 

 barytes. 



III. Gypsum from Southern Yorke Peninsula. 



Three varieties of gypsum are found genetically connected 

 with the salt lakes of Southern Yorke Peninsula. The follow- 

 ing details concerning these occurrences may be of interest, 



