PEOFBSSOR OWEN ON MACEOPUS. 443 ■ 



The fourth metatarsal (PL LXXXIIl. figs. 1 & 2, iv) is 6i inches in length, 1 inch 

 2 lines in breadth at the proximal end, 1 inch at the distal end (ib. fig. 13), 13 lines in 

 depth near the proximal end, decreasing to 5 lines near the distal trochlea. The upper 

 or anterior surface is convex across, and most so at the proximal half of the shaft, rising 

 to a low ridge near the joint with the tarsus. The lower or under surface is slightly 

 concave transversely at the distal two thirds, prominent and rugged at the proximal 

 third, where, toward the inner or tibial side it is developed into a low, thick, rough 

 ridge about an inch in length. It has coalesced with the proximal end of the third 

 metatarsal on the inner side, and presents a shallow channel with some rough surfaces 

 for the attachment of the proximal third of the fifth metatarsal on the outer side. 

 Above this attachment the fourth metatarsal sends backward a process presenting an 

 articular surface for the tarsal sesamoid (cut, fig. 2), above which is a grooved impress of 

 a peroneal tendon. The distal joint (PI. LXXXIIl. fig. 13) at its upper half is simply 

 convex vertically, almost flat across ; but at the lower half there is a median rising, or 

 ridge (a), causing two lateral surfaces concave across, and afi"ording a firm trochlear 

 joint to the proximal phalanx of the fourth toe (figs. 16, 17). Lengthwise the bone is 

 almost straight, with a feeble downbending of the distal articulation. 



The fifth metatarsal (ib. fig. 2, v, fig. 14) is compressed, or lamelliform, to near its 

 distal end, having a sigmoid flexure vertically, through an upbending of the proximal 

 expansion, while the rest and major part of the bone is bent in the opposite direction, 

 viz. downward, or backward (plantad). The proximal articulation (PI. LXXXIIl. 

 fig. 14) is an oblique flat triangular surface for that marked I on the cubo'ides (ib. fig. 12). 

 The lower border of the compressed shaft is thicker than the upper one, which is 

 almost trenchant along the proximal half. The outer surface has a shallow longitu- 

 dinal channel ; the inner one shows three rough facets, at its proximal fourth part, for 

 ligamentous attachment to the fourth metatarsal. The distal articulation is simply 

 convex, and chiefly so vertically. 



The digits correspond in size with their supporting metatarsals. The two diminutive 

 inner ones terminate each in an unguiculate phalanx, and are enveloped as far as this 

 joint in a common sheath of tegument, from which the two small claws protrude; they 

 are applied to dressing the hairy integument of the Kangaroo. 



Of the first phalanx of the fourth toe an upper (ib. fig. 16), an under (fig. 17), and 

 a proximal-end view (fig. 18) are given. An upper view of the second phalanx is given 

 at fig. 19. 



The last phalanx of the chief toe (iv) is elongate and conforms to the long, sharp- 

 pointed, straight, three-sided, bayonet-like claw, which forms the chief weapon of the 

 Kangaroo. The broad underside of this claw rests, like a hoof, on the ground ; the 

 smaller sheath of the ungual phalanx of the fifth toe has a similar quasi-ungulate 

 character. 



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