118 



COMPARATIVE OSTEOLOGY. 



The pectoral arch consists of three parts — the scapula, clavicle, and coracoii^ 

 bone. The scapula is sword-shaped, and placed nearly horizontally ; the 

 ■coracoid bone, the strongest of the three, is almost perpendicular, and firmly 

 attached to the sternum below, affording a strong basis for the bones of the 

 wing to move upon ; it helps to form the glenoid cavity for the humeras. The 

 clavicles project downwards and slightly forwards, arching inwards, and 

 generally becoming united below to form a flattened plate, the hypochideum / 

 ^he united clavicles are termed the furculum., familiarly known as the " merryw 



thought." The hypocleiueum is 

 usually joined by a ligament to the 

 sternum below ; in seme clnsses of 

 birds it is absent ; in some the 

 clavicles are not united ; in some, 

 again they are united by ossification 

 to the sternum. The ubia is larger 

 and stronger than the radius; the 

 carpus consists of two bones, the 

 metacarpus of three, one of which 

 33 a rudimentary pollex. There are 

 two digits, one of which has one, the 

 other two or three phalanges. 



The pelvis is expanded and shield- 

 like, -and consists of the ilium, 

 ischium, and pubis ; but there is 

 no inferior symphysis, and, therefore, no true pelvic cavity. The pubis is 

 styliform, and directed backwards and inwards ; in the ostrich alone it articu- 

 lates with its fellow. The femur is short, the tibia long, and anchylosed with 



Fio. 39. 

 ^ Pectoral arch of a Bird, sc, Scapula; co, cora- 

 eoid bone ; /, Clavicles, terminating below in the 

 hypocleideum ; gl. Glenoid cavity. 



Pelvis of a Bird 

 Acetabulum. 



A. Superior : B, Lateral aspect : sm, Sacrum : II, Ilium ; Is, Ischiv 



