of marriage on p. 282 of N.T.S.E.A. At the outset there was (i) the undivided commune, where any male could marry any female; this I call "absolute promiscuity." (ii) Then came the segmentation of the tribe into two exogamous moieties, and a man is restricted in his choice of a wife to half the women of the tribe. In practice we find these tribes have regulations which make their marriage customs identical with (iii) the four-class tribes which limit a man's choice to one-fourth of the women of a tribe; (iv) the cross-cousin marriages of these tribes are forbidden by the Dieri, whose rule is identical with that of the eight-class tribes, and limits a man's choice to one-eighth of the women of a tribe.
These three systems I term "limited" or "modified promiscuity," and I term the kinship circle into which a man may marry the "noa-group."
(v) The Dieri and a few other tribes have, side by side with the individual marriage common to all the Australian tribes, a system which provides accessory spouses for married persons or gives unmarried men certain rights over women who are not their individual wives. This is known as pirrauru, and I term the circle which enters into this relation by the name of the "pirrauru-group," or " circle," though it is, in fact, merely a fluctuating set of legal paramours; at most, kandri-made pirrauru seems to be permanent.
In order to make things quite clear I take a typical four-class tribe; not the Dieri, as both their kami-relation and other modifications (legal fictions for facilitating illegal marriages) complicate matters. In such a tribe one-fourth of the women are noa (i.e. potential wives) or marriageable to a given man. In the accompanying diagram the women of such a tribe are shown divided into the four classes: a male of class 4 (in a matrilineal tribe) has the women of class i as " father's sisters," of 2 as mother's sisters, of 3 as noa (potential
