THE SKELETON IN THE FLYING LEMURS. 201 



apophysis, occurs on the outer aspect of the bone just posterior to the 

 cuboidal articulation; this is intended for muscular insertion. 



Anteriorly, the face of the os calcis is entirely given over to a concavo- 

 convex articular facet for the cuboid, which presents a peculiarity, in 

 that it is conically hollowed on the planter border; into this fits a 

 pea-like articular process on the cuboid. On the under, or planter, side 

 of this the two bones are firmly lashed together by a broad tough liga- 

 ment. There would appear to be some special cause for the development 

 of a joint such as this, but the cause is not apparent. Internal to the 

 cuboid articulation there is a small facet for the scaphoid. Wlien the 

 two tarsal bones thus far described are articulated, and we view them 

 from what is really the outer side, we note that the plantar aspect of 

 the neck of the astragalus is oblique and arches over a similar groove 

 on the calcaneum, the two forming a foraminal passage through which 

 we can look. In the recent state this is filled up by the calcaneo- 

 astragaloid interosseous ligament, and is present in nearly all ordinary 

 mammals. 



The cuboid in Cynoceplialus is really more or less cuboidal in form; 

 its posterior articular face has already been described. It is also articular 

 in front where its slightly concave surface is divided by a ridge into two, 

 for the fourth and fifth metatarsals. There is a strong oblique groove 

 on its plantar surface, and this lodges the tendon of the peroneus 

 longus muscle. On its mesial aspect the cuboid makes an extensive 

 articulation with the scaphoid, and also the external cuneiform. Thus 

 it articulates with four bones : calcaneum. scaphoid, and the foiirth and 

 fifth metatarsals. 



Os naviculare, or scaphoid, is rather larger than the cuboid and its 

 posterior articulation is somewhat remarkable, for it not only articulates 

 with the head of 'the astragalus, but on its plantar aspect on the margin 

 of this articulation, it sends back a distinct process the side of which 

 articulates with the os calcis, and iipon which the plantar surface of 

 a part of the head of the astragalus rests. This process has a notch 

 on its outer side. Anteriorly," it has facets to articulate with the three 

 cuneiform bones. These are all more or less cuboidal in form, differ- 

 ing a little in the matter of size, and each articulates anteriorly with 

 the base of a metatarsal. The internal cuneiform is the largest and 

 joins the hallux metatarsal; it extends farthest to the front; the middle 

 one is the smallest, and the external one is between the tn'o in point of size. 



The three middle metatarsals very closely resemble the correspond- 

 ing bones in the hand, while in the foot a peculiarity is seen in hallux 

 metatarsal in that it has a conspicuous, rounded process erected on the 

 dorsal aspect of its extreme distal end. The articular surface in front 

 is carried upon this, affording the joint next beyond an unusual amount 

 of backward play in the vertical plane. 



