General Osteoiuy<j. 25 



synovial articulation with tlie proximal ends of radius and 

 ulna. The olecranal fossa is not always complete (cf. v. vi.), 

 nor is the internal condyle always imperforate (cf. v. vi. xiv.). 

 The Ulna is almost always longer than the radius (cf. iv. xiii, 

 1.), and generally provided with an olecranon (cf. xi.) of 

 variable size (cf. xiii.) : in those herbivorous quadrupeds 

 which are organised for rapid motion, both bones lie behind 

 each other, are immovably united, and more or less anchy- 

 losed. The Carpus consists usually of eight small bones, 

 ranged in a double row, varying in shape (cf. iii. xi.) and 

 number, but with this constant character, that the os unci- 

 forme always supports the two (when present, cf. Bpadypus) 

 outer metacarpals. The Metacarpus consists for the most 

 part of five separate (cf. xiii.) elongated bones : between the 

 metacarpals and the first row of phalanges are situated, very 

 generally, certain sesamoid bones (cf. viii, 1.). The number 

 of Phalanges in a finger rarely exceeds three (cf. xi.), and in 

 the thumb there are usually two. The number of fiugers 

 varies from one to five : of these five the third or middle 

 finger is the most constant, and commonly also the longest 

 (cf. viii, 1.) : the first or inner digit (the thumb) is the first to 

 disappear ; if there are two absent, the fifth or outer digit, 

 (the little finger) is the second to disappear : after these the 

 second, or index finger ; and then the fourth, or ring finger. 



lY. The Pelvic Arch and Appendages. The appendages of 

 the Pelvic Arch may be wholly wanting (cf. xii.) or rudi- 

 mentary. The Pelvis in other Mammalia is never so broad 

 as in Bimana, and its lateral walls are always smaller, flatter, 

 and longer. The Ilium seldom articulates with as many 

 sacral vertebrae as in Aves (cf. xii.). The Ischia and Pubes 

 are generally well developed. The pubic articulation (cf. iii. 

 iv.) is frequently very deep ; it is formed also by the ischia, 

 and is very often converted into bone. The Acetabulum is al- 

 most always complete ; and has frequently a depression for the 



