In the year 1839 Is. Geoff. St. Hilaire ¹) described and figured three species of his new genus Galidia, viz: elegans, concolor and olivacea, all natives of Madagascar. It seems that Galidia olivacea has not been captured by the travellers who visited Madagascar after Bernier and Goudot: the only specimen hitherto known was the type of which Is. G. St. Hilaire relates “la queue, dans notre individu, est incomplète; mais, à en juger par la portion très étendue qui est conservée, elle paraît plus longue que chez la Galidie concolore”, and therefore every one meant that the tail of the species in question would be as long as it is in Galidia eoncolor ²). The two other species are of frequent occurrence, especially Galidia elegans: some writers considered them as belonging to the same species, and the concolor as the young of the elegans; other authors agreed with Is. G. St. Hilaire in keeping the two species distinct. Is. G. St. Hilaire however already described the young of the elegans in the following terms “le jeune âge diffère de l’adulte par la couleur du dessus de son cou et de ses épaules, region qui est d’un roussâtre tiqueté de fauve, et par la nuance moins foncée et moins vive du rouge marron qui couvre le reste du corps. Les anneaux noirs de la queue sont aussi moins marqués.” Grandidier ¹) moreover remarks “le jeune et l’adulte ont la même coloration,” and Bartlett ²) states: “the colours of the young are exactly the same as in the adult.” Is. Gr. St. Hilaire had before him of the G. elegans several individuals and two skulls, of G. concolor a single skin without skull, and of G. olivacea a single mutilated skin with its skull. He accurately pointed out the differences between the skulls of elegans and olivacea, and figured the skull of the former. As nobody after him has spoken of the skull of G. concolor, and supposed that olivacea has a tail as long as in concolor, olivacea might just be the young of concolor, or the contrary might be the case. So, there are three questions to solve, viz: 1°. If there are differences between the skull of concolor and the skulls of the other species. 2°. How long the tail of olivacea is. 3°. How many species of Galidia we must admit.