MONOTREMATA. In _Echidna_ the carpus is broad, the scaphoid and lunar are united and there is no centrale. The pisiform is large and several other sesamoid bones occur. Each of the five digits is terminated by a large ungual phalanx. In _Ornithorhynchus_ the manus is more slender, but the general arrangement is the same as in _Echidna_. MARSUPIALIA. The carpus has no centrale and the lunar is generally small or absent. Five digits are almost always present. In _Choeropus_ however the only two functional digits are the second and third, which have very long closely apposed metacarpals; the fourth digit is vestigial, but has the normal number of phalanges, while the first and fifth are absent. The manus in _Notoryctes_ is extraordinarily modified, the scaphoid and all the distal carpalia are apparently fused, the first, second, and fifth digits are very small, the third and fourth, though having only one phalanx apiece, bear each an enormous claw. Lying on and obscuring the ventral surface of the manus is a large bone, probably a sesamoid. Among the EDENTATA there is a great diversity in the structure of the manus, the centrale is however always wanting, and except in _Manis_ the scaphoid and lunar are distinct. In the Sloths the manus is very long, narrow, and curved, and terminated by two or three long hooked claws, borne by the second and third, or the second, third and fourth digits. The fifth digit is absent, and the fourth is represented only by a small metacarpal. In the Anteaters the third digit is greatly developed and bears a long hooked claw. In _Myrmecophaga_ all five digits are fairly well though irregularly developed, in _Cycloturus_ the first, fourth, and fifth, are vestigial. In the Armadillos the manus is broad, and has strongly developed ungual phalanges. The digits, though almost always five in number, vary much in their relative arrangement. In _Dasypus_ they are regular, but are remarkably irregular in Priodon. The pollex is absent in Glyptodonts and in _Megatherium._ In _Megatherium_ the fifth digit is clawless while the second, third, and fourth bear enormous claws. In the Manidae the scaphoid and lunar are united; five digits are present, the third and fourth being very large, and all being terminated by deeply cleft ungual phalanges. In _Orycteropus_ the pollex is absent, while the other digits are terminated by pointed ungual phalanges. In SIRENIA the general structure of the manus is quite of the ordinary mammalian type. In _Manatus_ most of the bones of the carpus are distinct, but in _Halicore_ many, especially those of the distal row, have coalesced. The digits are always five in number and have the normal number of flattened phalanges.