In this paper several characteristics in the dentition of Australian Aborigines were compared with those of certain other populations from which the data were obtained by the present author. In addition, some other populations which had been studied by previous authors were also included for comparative studies on part of the dental characteristics discussed in this paper. The results are briefly summarized as follows:

1. The deciduous dentition in Aborigines, both males and females, shows the largest mesiodistal crown diameters among the five populations compared-Aborigines, Japanese, Pimas, Caucasians and American Negroes. However, the standard deviations in Aborigines are not significantly different from those of the rest of the populations.

2. The mesiodistal crown diameters of the permanent dentition in Aborigines were compared with those of Japanese, Pimas, Ainu, Caucasians and American Negroes. In general, Aborigines exceed most of the other populations in crown size as in the deciduous dentition. However, Aborigines are rather smaller than Pimas in some teeth. In males, for example, nine teeth out of fourteen represent larger mean values in Pimas than in Aborigines. The most striking difference is recognized in the maxillary canines in which the mean mesiodistal crown diameter in Pimas amount to 106.3% of that of Aborigines. Also in the mandibular canines, Pimas show 104.7% of Aborigines. As a whole, the overall tooth crown size in the deciduous dentition is the largest in Aborigines, but in the permanent dentition, Pimas exceed Aborigines in size of some teeth so that the latter does not necessarily have the largest tooth crown size among the modern human populations.

3. The shovel trait in the maxillary central incisors expressed in terms of depth of the lingual fossa is predominant in Pimas and Japanese, much less in Caucasians and American Negroes, and intermediate in Aborigines and Ainu.

4. Overall between-sex difference in mesiodistal crown diameters in the permanent dentition which is expressed by Mahalanobis' generalized distance shows that Aborigines are similar to Japanese in size component, but to Caucasians and American Negroes in shape component. In addition, Aborigines are quite different from Pimas in either size or shape components. A simple method of comparison reveals that almost the same trends are recognized in between-sex difference of the deciduous dentition.

5. Mesiodistal diameters in the molar crowns were compared between Yuendumu materials and the skulls obtained from Queensland. The average values are, both in males and females, insignificant between the two groups, except for the mandibular second molars in males. As a whole, both groups seem to be almost identical in this character; a minor discrepancy between the two groups appeared to be a random fluctuation.

6. Principal component analysis based on the mesiodistal crown diameters was carried out to reveal the characteristics in each population in terms of principal components. In particular, the present study is concerned with analysis of deciduous and permanent dentitions in combination. As a result, each population was characterized as follows: Aborigines represent the largest deciduous incisors and molars compared with the other populations, but the permanent incisors and premolars do not necessarily show the largest size among the populations compared; Japanese carry relatively larger deciduous molars; Pimas have the largest permanent incisors, both in absolute size and proportion, relatively small deciduous molars and large premolars; Caucasians generally represent the smallest tooth size, the maxillary lateral incisors being particularly small; and American Negroes carry the smallest deciduous incisors in absolute size and proportion.

7. Affinities between populations were analysed on the basis of Mahalanobis' generalized distance computed from mesiodistal crown diameters of the permanent dentition. The results reveal that Aborigines have a closer affinity to American Negroes and Pimas, relatively far from Japanese and Caucasians, and most far from the northern populations such as Ainu, Aleuts and Norwegian Lapps. In addition, the first canonical variates appear to distinguish the following four clusters in males: Aleut-Ainu cluster, Pima-Javanese-Japanese-Lapp cluster, American Negro-Aborigine cluster, and Swede-Caucasian-Tristanite-American White cluster. In the females, Aborigine-American Negro-Tristanite-Swede-Caucasian-American White cluster, Pima-Japanese-Javanese-Ainu cluster, and Aleut cluster may be distinguished.

8. In order to measure affinities in shape component, Penrose's shape distances were computed from mesiodistal crown diameters in the deciduous and permanent dentitions. Very interestingly, in the shape component, the permanent dentition of Aborigines is close to Caucasians, a little bit far from Japanese and American Negroes, and most far from the northern populations. On the other hand, shape distances in the deciduous dentition show a close affinity between Aborigines and Caucasians as well as Pimas. Although there are some discrepancies in shape distance between the permanent and deciduous dentitions and between males and females, it is noteworthy that Aborigines and Caucasians show in general close affinities in the shape component of tile crown measurements.

9. Six non-metric crown characters-shovel trait, cusp 6, cusp 7, deflecting wrinkle, protostylid and Carabelli's cusp-were observed and comparisons between Aborigines and some other populations were carried out on the basis of their frequency distributions. Distance coefficients devised by Smith were used as a tool for such a comparison. In the permanent dentition, Aborigines are close to Mongoloid populations and far from Caucasians, at least the non-metric crown characters are concerned. Trends observed in the deciduous dentition are also quite parallel to those of the permanent dentition. Based on Smith's distances, the following clusters may be distinguished: Aborigine cluster, Japanese-Ainu cluster, Pima-Eskimo cluster, Caucasian cluster and American Negro cluster.

10. From what we mentioned above, it may be concluded that affinities of Aborigines to the populations compared are different from character to character even if the investigations are focused on the dental characters. However, perhaps one fact which may be safely concluded is that Aborigines show a larger extent of archaic dental characters in almost every respect of the present study.

11. Relationship between Aborigines and Ainu was discussed on the basis of several findings obtained in the present study. The results reveal mat Ainu are located very far from Aborigines and very close to ordinary Japanese in almost every character such as absolute crown size and distance coefficients related to size and shape components of crown measurements, and frequency distribution of non-metric crown characters. This strongly supports conclusions obtained by several recent investigations on finger and palm print patterns, skulls and biochemical polymorphisms.