This form was founded on a femur found at Amboulitsate in W. Madagascar, and is described as follows: "It presents the same general characters, and evidently belongs to an _Aepyornis_, but to a different species, which we will call _Aepyornis medius_. The femur in question is not only distinguished by its lesser proportions but by the narrower external face of the bone; which variation results in causing the whole area between the trochanter and the base of the femoral neck to be much less depressed. The intermuscular line, which marks the insertion surface of the deep portion of the femoral triceps muscle, is hardly indicated, whereas it is very pronounced in the larger femur. The posterior side is also more rounded, and the distance which separates the popliteal depression from the proximal extremity is larger; the shape of this large depression is, however, the same as in the larger femur, and although the articular surfaces above it do show some differences, we know that these characters are not very reliable as they are subject to individual variations. Circumference of shaft 215 mm." Habitat: West Madagascar. {228} AEPYORNIS HILDEBRANDTI BURCKH. _Aepyornis hildebrandti_ Burckhardt, Pal. Abh. (VI) II, p. 127 (1893). I must refer my readers to Dr. Burckhardt's description, as it is too long and too technical to be reproduced here, especially as it is not comparative. I, however, give here some of his measurements:-- _Tibio-tarsus._ _A. grandidieri._ _A. hildebrandti._ Length 640 mm. 480 mm. Breadth at proximal end 190 " 130 " Breadth at distal end 135 " 82 " _Tarso-metatarsus._ Length circa 375 mm. 275 mm. Breadth at proximal end 145 " 103 " Breadth at distal end 145 " 95 " The locality of the type is Sirabé. Habitat: Madagascar. AEPYORNIS LENTUS M.-E. & GRAND. _Aepyornis lentus_ Milne-Edwards & Grandidier, C.R. CXVIII, p. 124 (1894). Original description as follows: "_Ae. lentus_ is remarkable from its short and massive feet. Length of tarso-metatarsus 360 mm. Width of proximal end 150 " Circumference of shaft 170 " Width of shaft 68 " " Habitat: Madagascar. {229} AEPYORNIS MULLERI M.-E. & GRAND. _Aepyornis mulleri_ Milne-Edwards & Grandidier, C.R. CXVII, pp. 124-125 (1894).