Dr. F. A. Bather — Studies in Edrioasteroidea. 



211 



agreement with the above characteristics and those of the latter group. 

 Its alumina is as high as that of the Australites. The alkalies are 

 low, but equally correspond with the position of the alkalies of the 

 Australites. There is also more agreement between the amount of 

 iron and magnesia of the Australites and the Brunei tektite than 

 between the latter and the Billitonites. Lime is irregular and 

 comparatively low in position. 



It is known that the quotient from the sum of iron and magnesia 

 divided by the sum of the alkalies, as well as the ratios of lime, potash 

 and soda are the evidences that distinguish the tektites from all 

 terrestrial rocks. Besides this, moreover, they also characterize each 

 group of the tektites, as is clearly shown in the following table 

 (Table III). It is evident from the diagram and also from this table 

 that the Brunei tektites do not correspond chemically with the 

 group of the Billitonites, but that there is much resemblance between 

 them and the Australites. 



Table III. 



Conclusions. — The tektites from Brunei in British Borneo are, 

 geologically speaking, most likely of diluvial age. Their shape and 

 sculpturing show nothing peculiar. Their physical properties 

 correspond with those of Billitonites. In their chemical composition 

 there is much resemblance between them and the Australites. 



IV. — Studies in Edrioasteroidea, VII. Morphology and Bionomics 



OF THE EDRIOASTERIDAE. 



By F. A. Bather, M.A., D.Sc, F.K.S. 

 Published by permission of the Trustees of the British Museum. 



rilHERE have now been described all the known members of the 

 i. Edrioasteridae and the very similar genus Steganollastus, as 

 well as a genus apparently connected with the Agelacrinidae but 

 presenting some remarkable features, namely Pyrgocystis. It is 

 proposed in this and the following Study to deal particularly with 



