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Show 1894.] ANATOMY OF ATHERURA AFRICANA. 679 The scapula is remarkable for the straightness of the axillary border, which always shows more or less of a curve in the other Porcupines. The metacromial process is flat and triangular and fairly broad at its base; it is situated at the extreme end of the spine, and the acromion is aborted beyond it. This arrangement is the same in Hystrix and Erethizon, but differs from Sphingurus, where the metacromion is some distance from the tip of the acromion. The humerus closely resembles that of Hystrix; it differs from that of the Tree-Porcupines in the patency of the supratrochlear foramen. The radius is more arched than in Hystrix, but less so than in the Tree-Porcupines. The grooves for the radial extensors of the wrist and the extensor ossis metacarpi pollicis are well marked. In the ulna the lower epiphysis is united to the shaft; it ends in a well-marked styloid process which fits like a pivot into the cuneiform bone. In adult specimens of Erethizon and Sphingurus the lower epiphysis of the ulna Avas separate. The first row of carpal bones consists of a scapho-lunar, cuneiform, and a large pisiform. The radial sesamoid lies across the palm and articulates with the scapho-lunar. The bones of the second row are normal except that, owing to the smallness of the unciform, the 5th metacarpal articulates largely with the cuneiform. The phalanges of the thumb are distinct as they are in Hystrix. In Erethizon and Sphingurus they are fused together. The os innominatum resembles that of Hystrix in the prominence of the anterior and posterior ventral spines (corresponding to the anterior superior and anterior inferior spines of human anatomy), in the length of the symphysis pubis, and in the pyriform shape of the obturator foramen. The iliac surface is narrow and looks downward. In the Tree-Porcupines the iliac surface is broader, the spines less marked, the symphysis shorter, and the obturator foramen more rounded. The femur of Atherura agrees with that of Hystrix and differs from that of the Tree-Porcupines in that the trochanters project more and the digital fossa is deeper. A third (gluteal) trochanter is only present in Efrethizon. There are two fabellae in Atherura. The tibia, as in all Porcupines, shows a prominent cnemial crest about the middle of the shin. The fibula is broad and flat above but soon becomes prismatic below • it articulates at both ends with the tibia and belowT Avith the astragalus. The tarsus shows a calcaneum singularly flattened from above downward, forming a very deep groove for the flexor longus hallucis. The navicular, as in all Porcupines, consists of two portions lyin" side by side; articulating with the inner one there is a large triangular bone, presumably the prehallux, which is folded under |