252 



(mudstone) only carry a trace of tin, the folds of quartzite 

 have a very fair percentage : one bed, 20 ft. thick, averages 

 over 1 per cent, of metallic tin, and is possibly the other leg 

 of the fold exposed on the northern side. The tin occurs in 

 narrow, sometimes hair-like, seams, running at right angles 

 to the strike of the folds, i.e., across the hill, and not along it. 

 From careful examination it seems evident that the tin was 

 deposited as alluvial tin, probably under sea or lake. The 

 occurrence on the south side of portions of several tin-bearing 

 folds, together with the width over which this deposit occurs, 

 indicates that the deposition was continued over a very consid- 

 erable period on an extensive scale. The folding, together with 

 metamorphic action that has taken place since its deposition, 

 may have led to some alteration in the position in which the 

 iSm occurs in the beds : to determine this a careful microscopi- 

 cal examination would be necessary. That tin-bearing rocks 

 were exposed and subject to extensive erosion during, or 

 prior to the Silurian age, is clearly evidenced by this dis- 

 covery, and should be of considerable interest to geologists as 

 well as mineralogists." 



Ordinary Meeting, April 5, 1910. 



The President (J. C. Verco, M.D., F.R.C.S.) in the 

 chair. 



Exhibits. — Mr. J. G. O. Tepper exhibited the larva of 

 a Queensland hawk-moth, Sequosa triangularis, and made 

 some observations on hawk-moths : also, galls of a species 

 of thrips, from the north-western district, on Acacia. The 

 galls contain 60 to 100 larvae each. Galls on Acacia am- era 

 at Broken Hill are so numerous that they bear the trees down. 

 Mr. Edquist exhibited Cuscuta ejnthyma, the dodder, found 

 growing on red clover at the High School, from which it 

 has spread to, and attacked, a native species of saltbush : 

 also, an estuarine bivalve mollusc, which was quite active 

 after eight days without water and exposed alternately in 

 the sun and shade. The specimens exhibited opened at once 

 on being ]olaced in sea water. Dr. Pulleine exhibited spiders 

 — Xephila, to show enormous disproportion between male and 

 female: Argyrocles commensal, in the webs of Xephila (from 

 Sydney) : Seleno cosmia, a gigantic earth-spider from Pichi 

 Richi Pass. Dr. Sweetafple exhibited a section of a chalce- 

 donized tree-trunk from the United States of America. Mr. 

 Howchin exhibited a group of Archceocyathincr from Wilson, 

 South Australia: and, as Editor, announced the completion 

 of part ii., vol. ii., of the Memoirs of the Society, on 

 Archceocpathince from the Cambrian of South Australia, by 

 T. Griffith Tavlor, B.Sc, B.A., etc. 



