28 EVERS'S COMPARATIVE ANATOMY. 



the clavicle, and the pubis the coracoid bone. Unlike the shoulder, 

 however, these bones are always anchylosed into one piece on 

 either side, and with one exception, never join in the mesial line ; 

 this single exception is afforded by the ostrich, in which the pubic 

 bones complete the pelvic circle by anchylosing" at their inferior 

 extremities. The vulture cinereus, and some acquatic birds, form 

 the nearest approach to this last condition. In them the pubic 

 bones are often surmounted by a cartilaginous appendix at their 

 anterior extremity. 



The ilium is the only bone of the pelvis that comes in contact 

 with the spine ; it is elongated in form, narrow in the centre, and 

 expanded at its extremities. This bone is anchylosed with the 

 sacrum, the ischium, and the spinous and transverse processes of 

 one or two dorsal vertebras. 



The ischium lies parallel with the ilium; it is a small oblong 

 bone, not presenting any peculiarity. 



The pubis unites with the ischium in a two fold manner in the 

 humming bird and some others, so as to form two foramina obtura- 

 toria, while in others, as the stork, it is only united to it at the coty- 

 loid foramen. This cavity is always incomplete at its internal part, 

 where it is closed by some fibrous bands. 



The femur is short, and slightly convex anteriorly; its head is 

 hemispherical, and joined to the shaft at a right angle, without 

 the intervention of a neck. There is but one trochanter; it is of 

 a large size, continuous with the external part of the shaft, and gene- 

 rally rises above the level of the head. The lower extremity of 

 this bone presents two condyles, the inner one for the tibia, the 

 outer one, which is longer and larger, rests on the tibia and fibula; 

 it is convex from behind forwards, and terminates in a groove in 

 both these directions. 



The tibia is the principal bone of the leg, the fibula ending in a 

 point inferiorly, and achylosed to the tibia for a considerable extent. 

 The lower extremity of the tibia forms a transverse trochlea, above 

 which there is a deep groove or foramen, to transmit the tendon of 

 the extensor digitorum communis. The upper and anterior part of 

 the tibia gives rise to a long pointed process, which ascends in the 

 shape of an olecranon in front of the joint, being also anterior to 

 the patella. 



The tarsus can only be recognised as a distinct segment of the 

 foot, when examined at an early period of the bird's existence ; 

 then only can be found a distinct astragalus of a flattened oval form, 

 convex superiorly, and concave below, where it meets the three 

 bones of the metatarsus partially separated. A rudiment of os calcis 

 may also be found in the extensor tendons. In the penguins, the 

 three metatarsal bones are only anchylosed at their extremities ; 

 but in other birds, faint grooves alone indicate their existence. 

 The remote extremity of the metatarsus presents three convex facets 

 to articulate with the toes. These last are subject to great variety 

 as to number, being reduced to two in the ostrich, and increased to 



