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Show 270 MESSRS. B. C. A. WINDLE AND F. G. PARSONS ON [Nov. 3, obturator foramen in the Horse, and this in spite of Lesbre's assertion to the contrary. In the Tapiridae, too (61), we failed to find it, and so did Murie (XVII.), who certainly would have been on the look out for it since he was the original describer. It is not described by any author in the Rhinocerotida?, but further observation is necessary here. In the Elephant no mention is made of it, though Miall and Greenwood (XXIX.) and Paterson and Dun describe the obturators somewhat carefully. With further opportunity for research we believe that it will be found that the obturator externus passes through the foramen in the Artiodactyla and Procaviida?, but that it does not do so in the Perissodactyla and Elephantidse. Quadratus femoris.-This muscle varies a good deal in size in different Ungulates, but it is usually present. Owing to the horizontal position of the pelvis, it passes obliquely from the tuber ischii to the back of the upper part of the shaft of the femur so as to form an X with the tendon of the obturator externus; it is usually somewhat constricted at its insertion, so that the name quadratus femoris used in human anatomy does not very aptly describe it. It is especially large in the Hyrax (74, 75), and in one Sheep (46) (see text-fig. 25) it was found to be double, but this does not seem to be always the case. Among the Perissodactyla it is not well developed ; in the Horse (63) it is quite smaU, and Meckel (VII.) says absent altogether. In the Tapir (61, 62) it is also small, while in the Rhinoceros (71) Haughton failed to find it *. In all the other animals on our list the muscle was present, and in the Duiker-bok, Sheep, and Harnessed Antelope was supplied by a branch from the sacral plexus as in Man. Muscles of the Posterior Femoral Region. Semimembranosus and Presemimembranosus.--These muscles have the usual mammalian attachments ; they are always fused at their origin from the tuber ischii; and it is characteristic of ungulates that this fusion continues much lower down the thigh than it usually does in other mammals. This is the case in the Hippopotamus (1), Pig (4, 11, 14), Chevrotain (21, 22), Deer (26, 29, 30), Ox (36, 40), Sheep (41, 46, 47), Goat (50, 52), Antelope (54, 55), Tapir (58, 61), Rhinoceros (71), Hyrax (74, 75), and Elephant (81, 84, 85). Meckel (VII.) and Lesbres (V.) point out that in the ruminants the origin is entirely ischial, while the Horse has a caudal origin besides ; we think that Ave are justified in broadening this generalisation and in saying that in the Artiodactyla there is only an ischial head, while in the Perissodactyla and Subungulata ischial and caudal heads are found (see text-figs. 24 & 26, S.M.). The semimembranosus has the usual mammalian insertion by a rounded tendon deep to the internal lateral ligament: in the * The dissection of this animal seems to have been carried out under great difficulties, so that the muscle 111.13- have been overlooked. |