20 BULLETIN 43, UNITED STATES NATIONAL MUSEUM. 



the two boues last named is the insignificant trapezoid. Owing to the 

 abruptly curved line formed by the heads of the metacarpals the 

 second and fifth bones lie at the level of the plane which would unite 

 the ends of the curve, 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 magnum. Thus the os 

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

 second and on the 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 represented 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 pisiform is also apparently absent. 



In Artibem the palmar x>art of the os magnum articulates with a 

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

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

 scarcely curved, and those of the second and fifth are disposed not 

 to approach each other. 



Among the vespertilionines we notice the following: Corynorhinus 

 closely resembles A r/i/^eft.s'. In Adelonycteris the trapezium possesses 

 a tubercle on the palmar aspect; the os magnum is without palmar 

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

 metacarpals approach each other and almost touch. In Atalapha the 

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

 the OS magnum is absent. Articuhxting on the pollical side of the fiftli 

 metacarpal bone is a separate ossicle, which appears to take the place 

 of the part last named. It is elongated and much larger tban auy of 

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

 much the same as Atalaplia; 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 Artibeus. 



The bone which articulates by its base with the fifth 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 



* The difficulty of studying the carpus without decalcification and makiug sec- 

 tions for microscopic study is conceded. The above epitome will doubtless be modi- 

 fied in details when such a method of study is adopted. The pteropines and true 

 rhinolophines are seen to be in alliance by characters derived from the carpus, a 

 position which is in harmony with the absence of the tragus aild the compact form 

 of the ©tic bones. 



