498 



ZOOLOGY 



SECT. 



carpals, so that it might readily be supposed that one of the 

 ordinary bones of the digit was absent. 



The pelvis of the American Anteaters is elongated, with a short 

 symphysis pubis. The ischia unite with the spinal column. There 

 is no third trochanter. The tibia and fibula are nearly straight, 



uln 



rad. 



acr 



FIG. 1074. Shoulder-girdle of Three-toed 



Sloth (Bradypus tridactylus). acr. acro- 

 mion ; cl. clavicle ; cor. coracoid. 



FIG. 1075. Right manus of Three-toed Sloth 



cun. cuneiform; hm. lunar; me 1 , first meta- 

 carpal ; mc5. rudiment of fifth metacarpal ; 

 pis. pisiform ; rod. radius ; sc. scaphoid ; trd. in. 

 trapezoid and magnum united. 



and parallel with one another. In Cydoturus the pes is modified 



to form a climbing organ. 



In the Sloths the pelvis is short and wide ; the spines of the 



ischia unite with the anterior caudal vertebrae so that a sacro- 



sciatic foramen is formed as in Anteaters. The femur is long 



and slender ; it is devoid of 

 third trochanter. The tibia 

 and fibula are also long and 

 slender. At its distal end 

 (Fig. 1076) the fibula develops 

 a peg-like process (x) which 

 fits into a depression in the 

 outer face of the astragalus. 

 The calcaneal process is ex- 

 tremely prolonged in Bradypus. 

 \nBradypus there is a tendency 

 to ankylosis between the tarsal 

 bones, and the proximal pha- 

 langes ankylose with the meta- 

 tarsals. 



In the Armadillos the pel- 

 vis (Fig. 1077) is extremely 

 long, and both ilia and ischia 

 are firmly fused with the 

 spinal column. The femur has 



a prominent third trochanter, The bones of the pes (Fig. 1078) 

 are normal. 



71CIV 



mesdc 



FIG. 1076. Pes of Three-toed Sloth, ast. 



astragalus ; cole, calcaneum ; cM. cuboid ; 

 fb. fibxila ; mesoc. mesoo ineif orm ; metat 1 . 

 'vestige of first metatarsal ; mttat 5 . vestige 



of fifth metatarsal ; nav. navicular ; til. 



tibia ; x, peg-like process at distal end of 



fibula. 



