The problem is to decide, given an African elephant's tooth, the position of that tooth in the series of six.
This has been done hitherto by reference to the “ridge formula” whose origin is discussed, and which is shown (a) to have been commonly misinterpreted, and (b) to have been inaccurate in any case.
The misleading results, including alleged evidence in support of the existence of a “pygmy” elephant, which resulted from this, are discussed.
It has been found impossible to construct a ridge formula which would be of any use in the determination of the position of a tooth in the series and other methods are proposed including the use of two new indices—the laminary index and the enamel-loop index.
The conclusion is arrived at that teeth numbers I and II may always be identified with certainty, number III with fair certainty, and number VI with much less certainty. Numbers IV and V are not at all easily to be distinguished.