Lord Derby obtained his first female Leucoryx in 1837, but it was not until the retirement of Mr. Cross from the Surrey Zoological Gardens and the consequent dispersal of that collection, some six or seven years afterwards, that he succeeded in acquiring a male. Owing to the age of the female at that time, although she bred twice with the male she failed to rear her offspring, and died in 1846, being then, as Lord Derby believed, the only female of this species in England. When the Derby Menagerie was dispersed in August 1851, the pair of Leucoryx Antelopes were among the animals selected by the Zoological Society of London, in virtue of Lord Derby’s bequest to them, and became the foundation of a stock which flourished for many years in the Regent’s Park Gardens. Young ones were bred of this pair or of their descendants in 1852, 1853, 1860, and 1864. Fresh examples of the Leucoryx were obtained by the Society in 1870 and 1880, and in 1881 a fine female was brought home and presented to the Menagerie by the late Mr. John M. Cook, F.Z.S. This Antelope has not done so well in the Regent’s Park of late years, but there is still one example of it living in the Menagerie, obtained last year, and it is hoped that a breeding pair may soon be re-established. An excellent figure of the adults of both sexes of the Leucoryx Antelope, drawn by Wolf from the Zoological Society’s specimens, was published in the first volume of Wolf and Sclater’s ‘Zoological Sketches.’ In the second volume of the same work a young one, likewise drawn by the same skilful artist, is represented on plate xix. The calf in question was born in 1851, and was about six months old when Mr. Wolfs water-colour drawing (from which fig. 93, p. 49, has been taken) was prepared. Lord Derby’s stock of the Leucoryx is said to have been received from Nubia, while others in the Zoological Society’s Gardens came from Senegal. We have not been able to recognize any difference between animals from these two countries, although they have been separated as distinct local forms (_nubica_ and _senegalensis_) by Wagner, and more recently by Herr Matschie as different species. There are at present no complete specimens of this Antelope in the British Museum, and skins of it fit for mounting both from Dongola and from Senegal are much required, in order that a strict comparison of examples from these widely distant localities may be made. The series now in the National Collection consists only of a mounted skeleton formerly in the Zoological Society’s Museum, a skin and skull of a young one from Sennaar, and some skulls and horns. Our Plate of this Antelope (Plate LXXXI.), which represents both sexes, was drawn on stone by Mr. Smit from a sketch prepared by Mr. Wolf, and probably represents the same animals as the plate in ‘Zoological Sketches’ above referred to. _May,_ 1899.