XII 



PHYLUM CHORDATA 



53 



the pubis, but by a small intercalated ossification, the 

 cotyloid bone. The ilium (it) has a rough surface for 

 articulation with the sacrum. Between the pubis (pub) in 

 front and the ischium (isch) behind is a large aperture, the 

 obturator foramen (obt). The femur has at its proximal 

 end a prominent head for articulation with the acetabulum, 

 external to this a prominent process, the great trochanter, 

 and internally a much smaller, the lesser trochanter, while 

 a small process or third 

 trochanter is situated on 

 the outer border a little 

 below the great trochan- 

 ter. At its distal end 

 are two prominences or 

 condyles, with a depres- 

 sion between them. Op- 

 posite the knee-joint, or 

 articulation between the 

 femur and the tibia, is a 

 small bone or knee-cap, 

 the patella. The tibia 

 has at its proximal end 

 two articular surfaces for 

 the condyles of the fe- 

 mur ; distally it has also 

 two articular surfaces, 

 one, internal, for the 

 astragalus, the other for 

 the calcaneum. The fibula is a slender bone which becomes 

 completely fused distally with the tibia. 



The tarsus consists of six bones of irregular shape 

 arranged in two rows, one of the bones, the navicular 

 (Fig. 303, nav), being intercalated between the two rows. 



Lepus cuniculus. Innominate 

 bones and sacrum, ventral aspect. acet, 

 acetabulum; il, ilium; isch, ischium; obt, 

 obturator foramen; pub, pubis; sacr t 

 sacrum; sy, symphysis. 



