462 THE PITTING OF FLINT-STTKFACES. [Aug. I9°9- 



27. The Pitting of Flint-Surfaces. 

 By Cecil Cakus-Wilson, F.K.S.E., F.G.S. (Eead May 26th, ] 909.) 



[Abstract.] 



Begular pittings of uniform size are occasionally seen on flints 

 which have been exposed to the weather. They have been referred 

 to by various authors, but no satisfactory explanation of their 

 origin has been given. The Author procured some interesting 

 examples occurring in a recent deposit near Folkestone. This 

 deposit is formed of materials which appear to have been washed 

 down from the adjacent Chalk hills. The flints appear to have 

 been derived from the sandpipes in the Chalk : their surfaces are 

 much decomposed. The removal of the colloid silica has rendered 

 them very porous, and they absorb a good deal of water. It is 

 believed that the pittings are due to mechanical action. Ohser- 

 vations and experiments carried out by the Author indicate that 

 such markings cannot have been produced by blows, nor by any 

 process of desiccation, and that the freezing of the absorbed water 

 seems to be the only satisfactory explanation to account for the 

 various details of the phenomenon. 



28. A New Species of Sthenvrus. 

 By Ludwig Glatjeet, F.G.S. (Bead June 1 6th, 1909.) 



[Abstract.] 



In a large collection of remains of extinct Marsupial mammals 

 from the Mammoth Cave, Margaret Biver (Western Australia), 

 the Author recognized several mandibles of a new kangaroo of the 

 genus Sthenurus. He now communicates a detailed description of 

 one specimen, and shows that the new species most nearly resembles 

 Sthenurus oreas (De Vis) and Sth. atlas (Owen). 



