On the other hand, the odd tens are formed in the ordinary vigesimal manner.

The reason for this anomaly is not obvious.

I know of no other number system that presents the same peculiarity, and cannot give any hypothesis which will satisfactorily account for its presence here.

In nearly all the examples given the decimal becomes the leading element in the formation of all units above 100, just as was the case in the Celtic scales already noticed.
Among the northern tribes of Siberia the numeral scales appear to be ruder and less simple than those just examined, and the counting to be more consistently vigesimal than in any scale we have thus far met with.

The two following examples are exceedingly interesting, as being among the best illustrations of counting by twenties that are to be found anywhere in the Old World.
TSCHUKSCHI.[352] 10.