This form of marriage exists among the western people of Torres Straits,[17] and is accompanied by features of the system of relationship which would follow from the practice. The mother’s brother is classed with the father’s sister’s husband as _wad-wam_, but there is an alternative term for the father’s sister’s husband and there was no evidence that the mother’s brother’s wife was classed with the father’s sister. It seemed possible that the classing together of the mother’s brother and the father’s sister’s husband was not a constant feature of the system of relationship, but only occurred in cases where the custom of exchange had made it necessary. The case, however, is sufficient to show that two of the correspondences which follow from the cross-cousin marriage may be the result of another kind of marriage. If we accept the social causation of such features and find these correspondences alone, it would still remain an open question whether they were the results of the custom of exchange or of the marriage of cross-cousins. The custom of exchange, however, is wholly incapable of accounting for the use of a common term for the mother’s brother and the father-in-law, for the father’s sister and the mother-in-law, or for cross-cousins and brothers- or sisters-in-law. It is only when these correspondences are present that there will be any decisive reason for inferring the former existence of the cross-cousin marriage. [17] _Rep. Cambridge Expedition to Torres Straits_, vol. v., pp. 135 and 241. The first conclusion, then, is that some of the features found in association with the cross-cousin marriage are of greater value than others in enabling us to infer the former existence of the cross-cousin marriage where it no longer exists. Next, the probability that such features as I am considering are due to the former presence of the cross-cousin marriage will be greatly heightened if this form of marriage should exist among people with allied cultures. An instance from Melanesia will bring out this point clearly. In the island of Florida in the Solomons it is clear that the cross-cousin marriage is not now the custom, and I could discover no tradition of its existence in the past. One feature, however, of the system of relationship is just such as would follow from the cross-cousin marriage. Both the wife’s mother and the wife of the mother’s brother are called _vungo_.