251 



Glenelg, where the large mass of coral was found, is on 

 the same parallel of latitude as King George Sound, where 

 it seems to have been in the first instance detected, and this 

 is not far from Cape Leeiiwin, which Tenison- Woods makes 

 the dividing-line between the tropical and extratropical 

 fauna. The South Australian examples probably migrated 

 from the West. There is reason to think that when the 

 sea returned to Gulf St. Vincent in Pleistocene times (after 

 the dry-land coiiditions of the later Pliocene) the water had 

 a higher temperature than at present. The raised sea 

 beaches of southern Yorke Peninsula and other places con- 

 tain many forms which are now extinct in our local waters, 

 as, for example, Barhatia (Area) trci'pezia, which occurs in 

 such numbers on the raised seabed of Port Wakefield that 

 its remains were used for ballasting the railway ; Meleagrina 

 inargaritifera, the ''pearl oyster" ; and immense numbers of 

 the large foraminifer, Orbitolites comjjlanata, which has its 

 habitat in warm seas. In Pleistocene times it is probable 

 that the entrances to the Gulfs were more restricted than 

 at present, which would act as a bar to the cold currents 

 from the south and raise the mean temperature of the water 

 in the laud-locked Gulfs. The large corallum obtained from 

 Glenelg must be of great age, and may possibly date from 

 a period of higher thermal conditions. 



Tenison-Woods named two species of Plesiastnea from 

 the Miocene of South Australia — P. St. Vinccnti from the 

 beds at Hallett Cove, and P. grandis from the Bunda 

 Plateau. Both specimens are fragments of considerable size, 

 but give no definite evidence of the actual size of the parent 

 mass. 



For the sketches reproduced in figs. 1 and 2 I am in- 

 debted to Miss Weir, who drew them under the direction of 

 her father, Captain Weir. 



Postscript. 



Subsequent to the reading of the above paper I received 

 an interesting letter from Captain Weir, in which, inter 

 alia, he says: — 'It may interest you to hear that I have 

 found another patch of coral about the same size and in 

 rather less water than that at Glenelg. About four years 

 ago a rock was reported off Port Parham, about 30 miles up 

 the Gulf on the east side, and a buoy was placed to mark 

 it. On Tuesday last I overhauled this buoy to put it in 

 order, and being a cjuiet day and the water clear I could see 

 the rock quite plainly, and noticed its general resemblance 

 to the one off Glenelg. I dragged a grapnel across it, and 



