There is no primitive race known to us which seems so fit to be selected as a type and standard of comparison in relation to cranial development, as the Aztecs or ancient Mexicans. They were the last dominant race among numerous native tribes, who, progressing from the rudimentary Stone Period, were excluded from influences such as those which in Europe superseded the ages of stone and bronze by the more perfect arts of civilisation. These changes archæologists are now agreed in associating with the introduction of iron. But if in this latter point also the parallel be admissible, then we must less conceive of the more perfect arts of civilisation being superinduced on those of the Archaic Period, than of the Allophylian nations being themselves superseded. More extended observations on the physical characteristics of these races will probably, to a great extent, determine this. Two skulls selected from Morton's Crania Americana are placed at the head of the table, and will afford a very satisfactory comparative estimate of the cranial capacity of the races of the Scottish tumuli. No. i. is figured in _Plate_ XVII. of Dr. Morton's valuable work, from which it will be seen that it decidedly belongs to the Brachy-kephalic class of Retzius, which again nearly corresponds with the pyramidal division of Dr. Prichard. It is thus described by Dr. Morton:--"With a better forehead than is usual, this skull presents all the prominent characters of the American race--the prominent face, elevated vertex, vertical occiput, and the great swell from the temporal bones upward." No. ii. is figured in _Plate_ XVIII. of the same work, and closely corresponds to it in type. It is described as "a remarkably well characterized Toltecan head from an ancient tomb near the city of Mexico, whence it was exhumed, with a great variety of antiques, vessels, masks, ornaments," &c. These, therefore, afford a fair comparative criterion of the capacity of the tumuli builders of Britain for the practice of arts analogous to those in which the later American races so greatly excelled at the epoch of the Spanish Conquest; and it will be seen that the comparison is, upon the whole, in favour of the superior intelligence of the British Brachy-kephalic race, as indicated by the cerebral mass and frontal development. No. 1. is an exceedingly interesting example of a skull of the Stone Period, in the Antiquarian Museum. It was found in 1822 in a rude cist in the parish of Banchory-Devenich, Aberdeenshire. On the top of the head is a hole nearly circular, rather more than an inch in diameter, which there can scarcely be a doubt was caused by the death-blow. In each corner of the cist lay a small pile of flint flakes.--No. 2 was taken from one of thirty cists found near Fifeness, in 1826, and described in a previous chapter.--Nos. 3, 4, and 5 were obtained from a group of rude cists discovered in the neighbourhood of Cockenzie, East-Lothian, in 1840. Nos.