Some australite structures and their origin (With Plate XXII.)

Abstract

A number of specimens of core-like australites possess well-developed flaked equatorial zones (text-fig. 1), on which peculiar grooves and flutings are present. These markings are here referred to as ‘bubble tracks’, the term indicating their apparent mode of formation. The specimens displaying these features are round and elongate forms. The round forms vary in diameter from 34 to 41 mm., the elongate forms range in length from 30 to 75 mm., while the weights vary from 27½ to 96 grams. Australites of these sizes are of infrequent occurrence, only twenty-one having been previously recorded (9, pl. 4), (2, pl. 4), and (3, pl. 9); the illustrations of these examples show that they have comparable features, such as flaked equatorial zones and bubble tracks.