PROFESSOR OWEN ON THE SPECIES OF PHASCOLOMYS. 497 
narrow tract (fig. 9, 5) with the tibial malleolar surface (fig. 8, d), and below with the 
surface articulating anteriorly with the cuboid and continued backward expanding 
(fig. 9, a) to rest upon and articulate with the calcaneum. 
The calcaneum (Pl. LXX. fig. 8, cl, and fig. 10) has three articular surfaces on its 
expanded tarsal or articular half:—one above, feebly convex, subtriangular in shape 
(fig. 10, a), for the astragalus; one anterior, concave (4), for the cuboid; and a narrow 
slip continued therefrom to the inner side of the bone for articulation with the scaphoid. 
The posterior fulcral or ‘sesamoid’ part of the bone (ib. c#) is triedral, broad, and 
convex below, concave on the inner side (fig. 10, c), toward which the lever (c#) is 
slightly bent, flat and rough on the outside: this part shows an oblong tuberosity (d) ; 
and there is a second, smaller, hemispheroid one (e) close to the cuboidal articular 
surface. 
Of the three cuneiforms the mid one (fig. 8, cm) is the smallest; their relations to 
the toes are shown in Pl. LXX. fig. 8. That with the scaphoid is analogous to, or 
homotypal with, the proximal relations of trapezium, trapezoides and magnum with 
the scapho-lunar in the carpus (Pl. LXX. fig. 5, ¢, z,m). The cuboid (fig. 8, 2), like the 
unciform (fig. 5, w), is the largest of the distal series. It presents a convexity behind for 
the astragalus and calcaneum, a small surface for the outer end of the naviculare, and 
expands as it advances to support part of the proximal ends of the fourth and fifth meta- 
tarsals, the latter sending outward an obtuse process beyond the proximal articulation. 
The ‘ pyramidale’ (ib. fig. 8, 0) has a slightly convex non-articular base, which is 
turned backward; the three sides of the cone are almost flat and articular; the under 
anterior one plays upon the hinder part of the upper articular surface of the astragalus, 
the upper one upon the hind end of the horizontal terminal articular surface of the tibia, 
the outer one upon the hind end of the malleolar surface of the fibula. 
The metatarsals progressively increase in length and breadth from that of the hallux 
(1) to the fourth (Iv); that of the fifth (v) is somewhat shorter, but is twice as thick as 
the fourth, and sends outward and backward a strong obtuse process from its outer 
and basal part. The hallux is reduced to one phalanx; the other toes have the usual 
number of phalanges, progressively increasing in thickness from the second to the outer- 
most, but in a slighter degree in 11. than in Iv. and y., thus showing a slight tendency 
towards the condition’ described in the ‘Cyclopedia of Anatomy and Physiology,’ 
vol, iii. (1841), Art. Marsupialia, p. 286, fig. 111. 
1 Flower, ‘ Osteology of the Mammalia, 12mo, 1870, p. 321.* 
