602 MR. R, I. POCOCK ON THE 



In Trichosiirus the conjoined second and third digits* are 

 much shorter than the fourth. The three lobes of the plantar 

 pad at the base of the terminal digits are in contact, the outer 

 lobe being larger than the other two taken together. The large 

 lobe of the hallux shows no trace of division, and there is a 

 tolerably well-defined, long external metatarsal pad reaching 

 from the heel almost to the plantar pad. 



The digits of Phalanger are approximately as in Trichosurios ; 

 but the external lobe of the plantar pad is separated to a certain 

 extent in front from the other lobes, which are fused although 

 defined by a groove, and are together larger than the outer lobe. 

 The entire hallux is relativel}^ larger than in Tt-ichosurus, and 

 its great pad is indistinctly divided ; there is no distinct external 

 metatarsal pad and the heel is shorter than in Trichosurus. 



In Pseudochirus the digits are as in the foregoing genera, but 

 all the elements of the striated pads on the sole are better defined 

 even than in Trichosurus. The outer lobe of the plantar pad is 

 completely isolated from the two conjoined inner lobes and about 

 balf their size. The great pad of the hallux is distinctly divided, 

 into a distal and a proximal portion, the latter repi'esenting the 

 inner metatarsal pad ; the outer metatarsal pad is well developed, 

 sharply defined, and about twice as long as wide. 



In the foregoing genera the hind foot is larger in every way 

 than the fore foot. 



In Phascolarctos the hind foot is not larger than the fore foot. 

 It differs from the hind foot of the other genera in having the 

 united second and third digits relatively much longer and only a 

 little shorter than the fourth ; the lobes of the plantar pad are 

 feebly differentiated, being fused to form a transveise cushion, 

 with irregularly convex anterioi' and irregularly concave posterior 

 border. The great pad of the hallux is undivided, and there is 

 no distinctly defined external metatarsal pad. Thus in the 

 development of the pads the foot of this genus differs more from 

 that of Pseudochirus than from that of Trichosuriis . 



The hind foot of Phascolomys, as has often been pointed out, 

 is a fossorial modification of the Plialangerine scansorial hind 

 foot, resulting from the conversion of the sharp, curved claws of 

 the latter into longer, stronger, and straighter claws, from the 

 approximate equality in length between the fourth and the united 

 second and third digits, the reduction in bulk of the great pad 

 of the hallux so that it projects only slightly beyond the inner 

 margin of the foot, with the terminal segment of the digit planted 

 like a hemispherical tubercle upon it, and from the practical 



* These two united digits act as a fuv-comb in Marsvipials. Possibly tliey were 

 primarily modified for that function. Generally they are too small in arboreal 

 forms to be of much use f"r grasping. But this cannot be maintained in the case 

 oi Phascolarctos ; and in Phascolomys they are large enough to be subservient to 

 digging. But in the Kangaroos thej' appear to be retained solely for the purpose 

 mentioned, and may frequentlj' be seen to be so employed. Moreover, it is signifi- 

 cant that these are the only digits in Tay'sipes which have other than rudimentaiy 

 claws. 



