The succeeding group of crania, Nos. 17-27, afford a fair average criterion of the Celtic type.--No. 17 is a skull dug up in a cave on the sea-coast, at the Mull of Kintyre, Argyleshire, near to where tradition affirms a battle to have been fought between the natives and an invading host of Northmen.--No. 18 is in like manner a memorial of Scandinavian aggression, and is marked in the catalogue of the Phrenological Museum as the skull of a Dane. It was dug out of the sand on the sea-beach, near Larnahinden, Argyleshire, where a party of Danes are believed to have landed and been defeated. It exhibits some remarkable measurements, especially in the small proportion of the vertical diameter; and a comparison of its various dimensions with those of the Roman skull, No. 16, brings out very distinctly the points of disagreement of two essentially different forms of crania. No. 18, however, is not to be accepted as a good Celtic type. The best medium form of the Celtic cranium is No. 20, which appears, in so far as the present amount of observation admits of such conclusions, to be a fair standard of this important class of crania. It forms one of a very interesting group of skulls in the Phrenological Museum. No. 19 was brought from Harray, near Lewis, and Nos. 20-24 from Iona. The whole of these were presented to the Society, in 1833, by Mr. Donald Gregory, Secretary of the Society of Antiquaries of Scotland, and they are each marked by him as the "Skull of a Druid from the Hebrides." They were no doubt obtained during the operations carried on by the members of the Iona Club, thus described in the introduction to the Collectanea de Rebus Albanicis:-- "In order to celebrate the institution of the Club, a meeting was held in the island of Iona, upon the 7th day of September 1833, permission having been obtained from His Grace the Duke of Argyle, the President, to make such excavations in the island as the Club might deem necessary. A search was made in the ancient cemetery called _Relig Oran_, for such tombstones as might in the process of time have been concealed by the accumulation of rubbish. The result of these operations was, that a considerable number of finely carved tombstones was brought to view, which none of the inhabitants had ever seen before."