PHYLUM CHORDATA 



467 



the femur, but the remainder of the cavity is bounded, not by the 

 pubis, but by a small intercalated ossification — the cotyloid bone. 

 The ilium (il^ 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 ohturator foramen (obt.). The femur is 

 rotated forwards when compared with that of the Lizard, so that 

 the limb is nearly in the same plane as the fore-limb, and the pre- 

 axial border is internal and the originally dorsal surface anterior. 

 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 trochanter. At its €rtzl- 



-ast 



CliTj- 



cu>et 



nau 



^c-un 



Fig. 1085.— LepuB cunieulus. Innominate 



and sacrum, ventral aspect, actt. acetabulum ; il. 

 ilium ; iidi. ischium ; obt. obturator foramen ; pw&. 

 pubis ; ioj^. sacrum ; iy. symphysis. 



Fig. 1086. — Iiepus cunieulus. 



Skeleton of pes. ast. astragalus ; 

 cal, calcaneum ; cuh. cuboid ; 

 cun. cuneiforms ; nav. navi- 

 cular. 



distal end are two prominences or condyles, with a depression 

 between them. Two small sesamoids or fabellm are situated 

 opposite the distal end on its posterior aspect ; and opposite the 

 knee-joint, or articulation between the femur and the tibia, is a 

 larger bone of similar character — the knee-cap or patella. The tibia 

 has at its proximal end two articular surfaces for the condyles of the 

 femur ; 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 (Fig. 1086) consists of six bones of irregular shape, 



■ VOL. II F F 



