316 PROCEEDINGS OF SECTION D. 



Mr. F. T. Gregory* has made known the leading physical and 

 geological features of this corner of Australia, which are shortly 

 as follows : — The principal portion consists of an undulating table- 

 land of granite, the western edge of which forms an abrupt 

 escarpment of from eight hundred to twelve hundred feet above 

 the sea ; its inland slopes are occupied with salt lakes. " Between 

 the western escarpment of the table-land, or Darling Range, and 

 the sea, lies a low belt of country from twenty to sixty miles in 

 width, the upper portion of which is evidently of very recent 

 formation." Near King George Sound, and along the south coast 

 near Mount Barren, are detached ranges up to three thousand 

 feet elevation. 



The same observer has further shown that the area occupied by 

 the principal forest trees corresponds with that of the littoral 

 tract, whilst the range of Xanthorrhteae is still moi'e contracted. 

 The line marking the 20-inch rainfall is one which embraces the 

 distinctive features botanically and physically of the tract exterior 

 to the granite table land, and is here employed as setting off the 

 Autochthonian Region from the Er-emian, the transition from one 

 to the other being remarkably rapid in a medial line, whilst the 

 blending of the two types is more prolonged on the west and south 

 coast, more so in the latter than in the former. 



As will hereafter be shown, the Autochthonian Region was greatly 

 extended in Pliocene times, and through the rainfall lines of twenty- 

 five and ten inches are narrowly separated, yet it is highly probable 

 that the Autochthonian types which occupy this intervening space 

 are remnants of the former extension of the main flora. 



The maximum rainfall is 46.67 (average of twenty years) at 

 Augusta, near Cape Leu win, diminishing to 35 at Perth, 19 at 

 Geraldton, and 5.5 at Carnarvon, increasing to 9.37 at Cossack, 

 and 32 at Derby. On the south coast, the chief rcords are — at 

 Albany, 32 ; at Esperance, 24.3 • at Eucla, 9. From Perth, the 

 rainfall rapidly diminishes in an easterly direction, and at York 

 (sixty miles off), the average of eleven years is 17.77. 



CHARACTERISTICS OF THE EREMIAN REGION. 



This botanic region has its centre at Lake Eyre, where the 

 average annual rainfall does not exceed five inches. This almost 

 rainless portion extends through four degrees of latitude ; the 

 rainfall is, moreover, very intermittent ; thus, at Charlotte Waters 

 the rainfall for 1881 was only 2.495 inches, whilst the average 

 for seven years is 7.064. But despite the high temperature and 

 limited rainfall, the region is not a desert as may be judged from 

 the large numher of plant species which occur ; and in this 



* Quart. Journ. Geol. Soc. 1861, xvii., p. 475, et seq. 



