332 CLASS XVI. 



The iliac bones in birds coalesce with the lumbar and sacral 

 vertebrae. They are elongate and deeply excavated on the surface 

 turned towards the abdomen, the cavities receiving the kidneys. 

 The spine-like pubic bones {ossa pubis) proceed backwards and are 

 not connected with each other, except in the ostrich. The ischiadic 

 bones {ossa ischii) are shorter and broader, they extend from the 

 cavitv of the hip-joint [acetabulum) backwards, parallel to the 

 pubic bones with which they coalesce at their extremity. Between 

 the pubic and ischiadic bones is left a large longitudinal aperture 

 [foramen obturatorium) , which is sometimes divided by a bridge 

 connecting the two bones into a smaller anterior and an elongated 

 posterior aperture. Another large aperture in the pelvis lies more 

 forwards and nearer the back, behind the acetabulum, between the 

 iliac and ischiadic bones [foramen {schiaticum) . 



The thigh-bone [femur) is shorter and thicker than the leg- 

 bone [tibia), nearly cylindrical, and slightly curved forwards; there 

 is a single trochanter, on the outside of the head of the bone, 

 which is large and projects above this head. In birds that cannot 

 fly, the Ostrich, Casuary, and Apteryx, in which the fore limbs 

 are so feebly developed, the thigh-bone is very strong and surpasses 

 the arm-bone (usually much longer) in thickness, and in the 

 Casuary and Apteryx in length also, remarkably. The tibia is 

 constantly the longest bone of the hind limbs; close to this bone 

 lies on the outer edge at the upper part a short and imperfect 

 fibula, which, coalescing with the tibia, terminates thin down- 

 wards, without extending to the tarsus. A knee-pan [patella) is 

 always, or almost always, present; in the Ostrich there are even 

 two, one above the other. 



In some water-birds [Colymbus Lath., Podiceps ejusd.) the 

 tibia terminates above in a pointed triangular process, keeled in 

 front, upon which in Fodiceps a patella also triangular lies, whilst 

 in Colymbus this process is broader, and seems to supply the place 

 of the absent patella^ The region of the tarsus and metatarsus is 

 represented by a single bone, of which the upper extremity strongly 

 resembles the head of the human tibia, and in which two cavities, 

 with a projecting line between them, receive the two articular 



1 Compare Meckel Syat. d.vergl. Anat. ii. s. 131, and E.Wagner in Heusingeb's 

 Zeitschr.f. d. organ. Physik. i. s. 586, Tab. xiii. 



