"'i89^i!''] PROCEEDINGS ()F THE NATIONAL MUSEUM. 19 



tlie two bones last named is the insigniticant trapezoid. Owing to the 

 ab'ruptly curved line formed by the heads of the metacarpals the 

 se(;ond and fifth bones lie at the level of the plane, which would unite 

 the ends of the curv<^, while the third and fourth form the bottom. 

 The cavity defined by the curve as indicated is almost entirely occupied 

 by a large hatchet-shape prolongation of the os nuignum. Thus the os 

 magnum, beside its axial attachments, is held on the one side to the 

 second and on tlui other to the fifth metacarpal bone. The heads of 

 these bones are so disposed as not to approach each other. The pisi- 

 form is absent unless it is rei)resented in the palmar prolongation of 

 the OS magnum. 



In rhinolophines the plan is that of pteropines. Though the bones 

 are less massive than in that group, the methods of articulation are 

 the same, and the i)isiform is also apparently al)sent. 



In Art ibeus t\ni palmar part of the os magnum articulates with a 

 separate but much smaller element, which occupies the place of the 

 hatchet-shape plate in Fteropm. The heads of the metacarpals are 

 scarcely curved, and those of the second and fifth ;ii-e disposed not 

 to approach each other. 



Among the vespertiliouines we notice the following: dori/norJuHus 

 closely resembles ArUhens. In Adelomjcteris the trapezium ])ossesses 

 a tubercle on the palmar as])ect; the os magnum is without palmar 

 plate either united or separate. The heads of the second and fifth 

 metacarpals approach each other and almost tcuich. In Atalapha the 

 tubercle to the trapezium is retained, while the palmar extension of 

 the OS magnum is absent. Articulating on the pollical side of the fifth 

 metacarpal bone is a separate ossicle, which a,i)pears to take the place 

 of the part last named. It is elongated and much larger than any of 

 the carpal elements. I have named it the pisiform. Antrozoiis is 

 much the same as Atalapha; the ossicle by the side of the fifth meta- 

 carpal bone is triangular in shape. The plate of bone which is con- 

 tinuous with the OS magnum on its palmar aspect in pteropines appears 

 to be the same as the separate ossicle in the same situation in Artihcm. 



The bone which articulates by its base with the iifth metacarpal bone 

 in Atalapha and Antrozous would appear to be identical with the above 

 plate, since when it is i)resent the os-magnum ends in a simple manner 

 toward the palm. It would appear to be the pisiform, since in Atalapha 

 it was observed to receive the tendon of the extensor carpi ulnaris. 



Sesamoid hones. — The sesamoid bones are found in locations where 

 great motion is permitted on the side opposite to which the bones are 

 lodged — the purpose being apparently to prevent stretching of the 

 muscles which carry the sesamoids. At the point at Avhich stretch- 

 ing would begin the l)<)nes lock with the joint surface and takes the 

 strain. They are best developed on the dorsum of the carpus in phyl- 

 lostomines. 



The tendency above noted for the second and fifth metacarpal bones 

 to incline toward one another on the palmar aspect of the carpus, and 



