86 THE COMMON FROG. [chap. 



monkeys of America and certain long-tailed monkeys 

 {Colobi) of Africa, are thumbless. 



In man, when standing, the weight of the body is 

 transferred to the limbs by a large bony girdle which, 

 from its basin-like shape, is called the pelvis. This 

 basin consists of the two haunch-bones which meet 

 together in front, but behind are separated by the 

 lower part of the backbone (called the sacrum), to 

 which the haunch-bones are attached, and which 

 forms the hinder portion of the pelvis. The pelvis 

 has a depression, or "socket," on each side, into which 

 fits the head of one of the thigh-bones. Each 

 " haunch-bone " consists of three parts, which are, in 



Fig. 51. — Outer side of os innominatum of Man. a, acetabulum ; at, anterior inferior 

 spinous process of the ilium ; as, anterior superior spinous process of the ilium ; 

 c, crest of fhe ilium : ij>, ilio-pectineal eminence ; o, obturator foramen ; J>, pubis 

 — its horizontal ramus ; posterior inferior spinous process ; ps, posterior superior 

 spinous process ; s, spine of the ischium ; t, tuberosity of the ischium. 



man, primitively distinct, but afterwards anchylose 

 together, and all three elements (in each haunch-bone) 

 take a share in the formation of the bony thigh-socket 

 or acetabidum. These three elements are named — 

 I, ilium ; 2, ischium; and 3, piibis. It is the ilium 



