147 



flat. The second phalanx in the Opossum supports a claw, but in 

 the Phalangers is short, transverse, unarmed, and almost obsolete. 



" In all the preceding genei-a there are two small sesamoid bones 

 on the underside of the joints of the toes, both on the fore and hind 

 feet. 



" The commencement of a degeneration of the foot, which is pecu- 

 liar to, and highlv characteristic of, the Marsupial animals, may be 

 discerned in the Petaurists, in the slender condition of the second 

 and third toes, as compared witli the other three. In the Phalangers, 

 this diminution of size of the second and third toes, counting from 

 the thumb, is more marked. I'hey are also both of the same length, 

 and have no individual motion, being united together in the same 

 sheath of integument as far as the ungueal phalanges, whence the 

 name of Phalangista applied to this genus. In the saltatorial genera 

 of Marsupiata the degradation of the corresponding toes is extreme, 

 but though reduced to almost filamentary slenderness, they retain 

 the usual number of phalanges, the terminal ones being armed with 

 claws, which appear as appendages at the inner side of the foot, for 

 the purpose of scratching the skin and dressing the fur. In the Kan- 

 garoos and Potoroos the innermost toe is deficient, but in the Pera- 

 meles it is retained. In Per. lagotis I find the metatarsal bone of this 

 toe supports only a single rudimental phalanx, which reaches to the 

 end of the next metatarsal bone, and the internal cuneiform bone 

 is elongated. In Per. grisea the internal toe is as long as the 

 abortive second and third toes, and has two phalanges, the last of 

 ■which is divided by the longitudinal fissure characteristic of the un- 

 gueal phalanges in this genus. The power of the foot is concen- 

 trated in all these genera on the two outer toes, but especially the 

 fourth, which in the great Kangaroo is upwards of a foot in length, 

 including the metatarsal bone and the claw, which latter resembles an 

 elongated hoof, but is three-sided, and sharp-pointed like a bayonet. 

 It is with this formidable weapon that the Kangaroo stabs and rips 

 open the abdomen of its assailant ; it will hold a powerful dog 

 firmly during the attack with the anterior extremities, and sup- 

 porting itself behind upon its powerful tail, deliver its thrusts with 

 the whole force of the hinder extremities. The cuboid bone which 

 supports the two outer metatarsals in the Kangaroo is proportion- 

 ally developed. The internal cuneiform bone is present, though 

 the toe which is usually articulated to it is wanting. It is also the 

 largest of the three, and assists in supporting the second metatarsal ; 

 behind it is joined with the naviculare and external cuneiform ; the 

 small middle cuneiform occupying the space between the external and 

 internal wedge-bones and the proximal extremities of the two abor- 

 tive metatarsals. The great or fourth metatarsal is straight and 

 somewhat flattened ; the external one is compressed and slightly bent 

 outwards ; the toe which this supports is armed with a claw similar 

 to the large one, but the ungueal phalanx does not reach to the end 

 of the second phalanx of the fourth toe, and the whole digit is pro- 

 portionally weaker." 



