In October, 1921, the Spanish newspaper _La Prensa_, New York, published a short account, received by letter from the City of Mexico, describing what purported to be an extraordinary discovery made early in the autumn. It related to the finding of a stone mask decorated in mosaic, discovered by one of the assistants of the Museo Nacional in a sepulchral chamber in Guerrero. This mask was described as being about eight inches high, the human face being partly covered with an incrustation of small pieces of turquois, with small bits of coral shell above the eyebrows and below the nose. Each eye was formed by an oval piece of pearl shell, with pupils of hematite. The mosaic covering was missing from the upper part of the forehead and the chin. The newspaper _Excelsior_ of Mexico City, under date of October 20, 1921, published a photograph of the specimen and a detailed study of the object in a statement signed by José María Arreola, a member of the staff of the Department of Anthropology in the City of Mexico. In this statement Arreola casts doubt on the authenticity of the specimen, pointing out that none of the known pieces of mosaic-work in European collections are of stone; that the surface of the mask is polished, which would make it difficult for the incrustation to have adhered during centuries of burial; that there are no traces of dirt in the cracks between the pieces of turquois, and finally he calls attention to a strong odor of glue which pervades the object. These arguments seemed sufficient to cast serious doubt as to the genuineness of the mosaic decoration of the mask. No such question was raised in regard to the mask itself. In a brief article entitled “Una Mascara de Mosaico Falsificada,” published in _Ethnos_ (nos. 8-12, dated Mexico, Nov. 1920-Mar. 1921), the same writer categorically asserts that the specimen is fraudulent, and calls on the reputed finder, Sr. Don Porfirio Aguirre, to present the evidence regarding the exact place where the specimen was discovered in order that further excavation may be made with a view of establishing beyond question the history of such an important and unique discovery.[79] [Illustration: PL. XIX MASK OF HUMAN SKULL WITH MOSAIC DECORATION BRITISH MUSEUM, LONDON] Precious and semi-precious stones were occasionally inserted singly for decorative purposes. In this respect we may simply refer, in passing, to the custom in ancient Mexico and Central America of decorating the teeth by inserting inlays in the upper incisors, turquois, jadeite, hematite, obsidian, and rock-crystal having been used in such manner. Rarely two, and in one instance three, insets have been found in a single tooth; but this form of decoration can in no sense be considered as mosaic.[80]