(2) The Chellean implements, which precede those of Mousterian type, are commonly associated with a fauna of southern affinities. This denotes an inter-glacial period. Therefore an inter-glacial period is indicated as having preceded the Mousterian age. But after the Mousterian age, none of the subsequent types are associated with a 'southern fauna.' Indications are thus given, to the following effect. The Mousterian position is such that a distinct inter-glacial period should precede it, and no such definite inter-glacial period should follow it. The last glacial period alone satisfies these requirements. The Mousterian position therefore coincides with the last great glaciation, whether we term this the fourth (with Professor Penck), or the third, with Professor Boule. (3) The Mousterian industry characterises a Palaeolithic settlement at Wildkirchli in Switzerland: the position of this is indicated with great accuracy to be just within the zone limited by the moraine of the last great glacial period (Penck's No. IV or Würmian). The associated fauna is alleged to indicate that the age is not post-Würmian, as might be supposed. This station at Wildkirchli probably represents the very earliest Mousterian culture, and its history dates from the last phase of the preceding (_i.e._ the Riss-Würm) inter-glacial period. But it belongs to Penck's glaciation No. IV, not to No. III. (4) Discoveries of implements of pre-Mousterian (Acheulean) form in the neighbourhood of the Château de Bohun (Ain, Rhone Basin, France, 1889), and Conliège (Jura, 1908) are accompanied by stratigraphical evidence whereby they are referred to an inter-glacial period later than the Riss glaciation (Penck's No. IV, Boule's No. III). The remaining arguments are directed against the position assigned by Professor Penck to the Mousterian implements. (5) Professor Penck admits that the epoch of the Mousterian type was glacial, and he recognises that it was preceded by a definitely inter-glacial epoch, with a southern fauna. But by selecting his No. III as the glacial period in question he is led to postulate a subsequent but warmer inter-glacial subdivision of the Mousterian period. The difficulty is to find convincing evidence of this post-Mousterian inter-glacial period, and of the corresponding 'southern' fauna. Professor Penck believes that the 'southern' animals returned. Professor Boule can find no post-Mousterian evidence of such a fauna. The constituent forms became extinct or migrated southwards, never to return. If this contention be true, and there is much in its favour, Professor Boule's view must be adopted.