THE SKELETON IN THE FLYING LEMURS. 199 



on its outer. The shaft is smooth, compressed from within, outward, 

 and very gradually increases in caliber toward its malleolar extremity. In 

 one specimen (3) this bone is deeply and longitudinally grooTed for 

 the entire upper one-third of -its tibial aspect. 



Bulbous in shape, its distal end forms the external malleolus, being 

 obliquely truncate from above, downward, and outward; the inner surface 

 is given over to the facets for articulation with the tibia and the astragalus 

 of the foot. Above this is a distinct little process for ligamentous attach- 

 ment. There is another, but larger, tubercle on its outer aspect. Liga- 

 ments of the ankle are also attached at a few other points; in fact, the 

 most important function of this bone in Cynoceplialus is to assist in 

 completing this very essential joint. 



Pes contains the same number of metatarsals as manus contains meta- 

 carpals, and the toes the same number of phalanges as we find in the 

 hand ; that is, three Joints in all the toes with but two in hallux. 



The study of the foot of Gynocephalus is wonderfully interesting. 

 Owing to the unusual way the member has been used and ontogenetically 

 evolved, it has the appearance, on first sight, of having been dislocated. 

 The articulatory part of the astragalus which articulates with the tibia, 

 and to some extent the bone itself, has rotated inward and to a degree 

 forward, so that the longitudinal axis of this long and narrow foot makes 

 a varying angle with the continuity of the shafts of the bones of the leg. 

 This angle in the vertical plane may range all the way from 120° through 

 a right angle to an acute one of 70°, according to the manner in which 

 the animal holds its foot. The member possesses also a certain amount 

 of motion either backward and forward, when the limb is held away 

 from the body, or inward and outward, when it is brought near the latter 

 and the efl^ort is made to move the foot in those directions. 



Flower -" states, and it is true, that "The liones of the tarsus of mam- 

 mals present fewer diversities of number and arrangement than those of 

 the carpus." Cynoceplialus offers no exception to this rule. 



There are seven bones in the tarsus of the colugo, namely the astragalus, 

 the OS calcis or calcaneum, the scaphoid or navicular, the three cuneiforms 

 (internal, middle, and external), and the cuboid. This enumeration does 

 not take into consideration the presence of several important sesamoids 

 which will be noticed farther on. 



The astragalus of all the tarsal bones is next in size to the os calcis, 

 the latter being the largest bone of the foot. In man this bone receives 



-° Osteology of the Mammalia, 340. Many works have been 'examined in this 

 connection, and the literature of the subject is very extensive, but it would 

 appear that no author as yet lias produced sufficient evidence to warrant any 

 radical change in the nomenclature of the tarsal bones, or to set aside their 

 homologies as they have long been given in standard treatises on anatomy. 

 104558 3 



