147 



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

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



" In all the pi-eceding genera 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 highly characteristic of, the Marsupial animals, may be 

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

 and third toes, as compared \vith the other three. Inthe Phalangers, 

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

 the thumb, is more marked. They are also both of the šame length, 

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

 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 terminai ones being armed with 

 claws, ■vvhich 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- 

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

 toe supports only a single rudimentai 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 lašt of 

 ivhich is divided by the longitudinal fissure characteristic of the un- 

 gueal phalanges in this genus. The po\ver of the foot is concen- 

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

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

 including the metatarsal bone and the cla\v, which latter resembles an 

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

 It is -vvith this formidable \veapon that the Kangaroo stabs and rips 

 open the abdoraen of its assailant ; it w\\\ hold a powerful dog 

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

 porting itself behind upon its powerful tail, deliver its thrusts \vith 

 the •vvhole force of the hinder extremities. The cuboid bone \vhich 

 supports the two outer metatarsals in the Kangaroo is proportibn- 

 ally developed. The internal cuneiform bone is present, though 

 the toe \vhich is usually articulated to it is ■vvanting. It is also the 

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

 behind it is joined \vith the navdculare and external cuneiform ; the 

 small middle cuneiform occupying the space between the external and 

 internal ^vedge-bones and the proximal extremities of the two abor- 

 tive metatarsals. The great or fourth metatarsal is straight and 

 some-what 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 \vhole digit is pro- 

 portionally weaker." 



