_Male._ _Female._ 1. Ippai. 1. Ippata. 2. Kumbo. 2. Buta. 3. Murri. 3. Mata. 4. Kubbi. 4. Kapota.
All the Ippais, of whatever gens, are brothers to each other. Theoretically, they are descended from a supposed common female ancestor. All the Kumbos are the same; and so are all the Murris and Kubbis, respectively, and for the same reason. In like manner, all the Ippatas, of whatever gens, are sisters to each other, and for the same reason; all the Butas are the same, and so are all the Matas and Kapotas, respectively. In the next place, all the Ippais and Ippatas are brothers and sisters to each other, whether children of the same mother or collateral consanguinei, and in whatever gens they are found. The Kumbos and Butas are brothers and sisters; and so are the Murris and Matas, and the Kubbis and Kapotas respectively. If an Ippai and Ippata meet, who have never seen each other before, they address each other as brother and sister. The Kamilaroi, therefore, are organized into four great primary groups of brothers and sisters, each group being composed of a male and a female branch; but intermingled over the areas of their occupation. Founded upon sex, instead of kin, it is older than the gentes, and more archaic, it may be repeated, than any form of society hitherto known.
The classes embody the germ of the gens, but fall short of its realization. In reality the Ippais and Ippatas form a single class in two branches, and since they cannot intermarry they would form the basis of a gens but for the reason that they fall under two names, each of which is integral for certain purposes, and for the further reason that their children take different names from their own. The division into classes is upon sex instead of kin, and has its primary relation to a rule of marriage as remarkable as it is original.
Since brothers and sisters are not allowed to intermarry, the classes stand to each other in a different order with respect to the right of marriage, or rather, of cohabitation, which better expresses the relation. Such was the original law, thus:
Ippai can marry Kapota, and no other. Kumbo " " Mata, " " " Murri " " Buta, " " " Kubbi " " Ippata, " " "
This exclusive scheme has been modified in one particular, as will hereafter be shown: namely, in giving to each class of males the right of intermarriage with one additional class of females. In this fact, evidence of the encroachment of the gens upon the class is furnished, tending to the overthrow of the latter.