It is not without some hesitation that we refer to a separate genus those species of Tragelaphine Antelopes (hitherto placed in _Tragelaphus_) which have undergone certain special modifications of structure in adaptation to a semi-aquatic mode of life. In the species of _Tragelaphus_ discussed in the preceding part of this work, as well as in all the other genera of Tragelaphinæ, the feet adhere to the digitigrade type characteristic of most of the ruminant artiodactyle Ungulates, retaining the short narrow hoofs and strong elastic ankles fitted for easy and swift progress over the firm soil of the veldt or woodland. In the species of _Limnotragus_, on the contrary, the feet are furnished with hoofs of relatively enormous length, which spread far apart at every step, and are obviously designed to enable their owner to pass over the soft soil of marshes and river-banks without sinking deeply into the ground. This modification is accompanied by an increase in the flexibility of the ankle-joints, which are capable of yielding to the weight of the body, so as to allow the false-hoofs and the smooth tough horny skin at the back of the pasterns to rest upon the soil, and thus to further augment the supporting area of the foot. It is these peculiarities in the structure of the feet, in conjunction with a length of limb exceeding that of other Tragelaphines, which impart to the species of _Limnotragus_ that characteristic semiplantigrade aspect and that unusual awkwardness of gait so noticeable in these Antelopes when walking upon firm resisting ground. Up to the present time three species referable to this genus have been described, namely, _L. spekii_ from E. Africa, _L. gratus_ from Tropical West Africa, and _L. selousi_ from the valley of the Zambesi. Unfortunately there are not at present available materials from the different parts of the area over which the genus ranges, sufficient to enable us to determine satisfactorily the exact value to be assigned to these three forms. Consequently, although the evidence, so far as it goes, tends to show that the characters upon which they have been based may ultimately prove to have merely a subspecific importance, we prefer, for the time being, to allow them to take the rank that was originally assigned to them by their respective describers, and to arrange them as three species. _Range of the Genus._ Congo Valley and Lake-districts of Southern and Eastern Africa. The three species may be shortly distinguished as follows:— _a_. Size smaller; height at withers about 36 inches: sexes dissimilar; male blackish, female rufous 127. _L. spekii._ _b._ Size larger; height at withers about 40 inches. _a1._ Sexes similar, blackish 128. _L. selousi._ _b1._ Sexes dissimilar; male blackish brown, female red. 129. _L. gratus._