208 SKELETON OF THE KANGAROO. 



femur, wliicli makes these muscles operate upon that lever 

 at a most advantageous angle ; the trunk, borne along in 

 the violent leaps, needs to be unusually firmly bound to- 

 the pelvic basis of the chief moving powers. Accord- 

 ingly, we find a pair of bones, 64', extending forwards 

 from the pubic symphysis, 64, along the ventral walls, 

 giving increased bony origin to the unusually developed 

 median abdominal muscles attaching the thorax to the 

 pelvis ; and these " marsupial bones," as they are called, 

 have accessory functions relating to reproduction in both 

 sexes of the marsupial quadrupeds. The femur, 65, is 

 more than twice the length of the humerus ; it is propor- 

 tionally strong, with well-developed great and small 

 " trochanters," and a " fabella" behind one or both con- 

 dyles. The patella is unossified. The fibula, 67, is im- 

 movably united to the lower half of the tibia. This 

 bone, QQ^ is of unusual length and strength, and is firmly 

 interlocked below with the trochlear astragalus. The 

 heel-bone sends backwards a long lever-like process for 

 the favorable insertion of the extensors of the foot. This 

 member is of very unusual length. The innermost toe, 

 or hallux, is absent ; the second and third toes are ex- 

 tremely slender, inclosed as far as the ungual phalanx in a 

 common fold of integument, and reduced to the function 

 of cleansing the fur. The offices of support and progres- 

 sion are performed by the two outer toes, w and f, and 

 principally by the fourth, which is enormously developed, 

 and terminated by a long, strong, three-sided, bayonet- 

 shaped claw ; these two toes are supported, as usual, by 

 the OS cuboidcs, which is correspondingly large, whilst 

 the naviculare and the cuneiform bones are proportion- 

 ally reduced in size. The bones of the fore-limb, though 

 comparatively diminutive, present all the compl^ xities of 



