530 



ZOOLOGY 



SECT. 



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, 



rad. 



acr 



FIG. 1143. Shoulder-girdle of Three-toed 



Sloth (Bradypus tridactylus). acr. aero- 

 mion ; cl. clavicle ; cor. coracoid. 



FIG. 1144. Right nianus of Three -toed Sloth. 

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

 carpal ; mc5. rudiment of fifth metacarpal ; 

 pis. pisiform ; rad. radius ; sc. scaphoid ; trd. m. 

 trapezoid and magnum united ; uln. ulna ; unc. 

 unciform. 



and parallel with one another. In Cycloturus 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 sacro- 



sciatic foramina are 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. 1145) the fibula develops 

 a peg-like process (V) which 

 fits into a depression in the 

 outer face of the astragalus. 

 The calcaneal process is ex- 

 tremely prolonged in Bradypus, 

 in which there is a tendency 

 to ankylosis between the tar- 

 sal bones, and the proximal 

 phalanges ankylose with the 

 metatarsals. 



In the Armadillos the pelvis 

 (Fig. 1146) is extremely long, 

 and both ilia and ischia are 

 firmly fused with the spinal column. The femur has a pro- 

 minent third trochanter. The bones of the pes (Fig. 1147) are 

 normal. 



rrtetal.1 



FIG. 1145. Pes of Three-toed Sloth, ast. 

 astragalus ; calc. calcaneum ; cbd. cuboid ; 

 fb. fibula ; mesoc. mesocuneiform ; metafi. 

 vestige of first metatarsal ; metat 5 . vestige 

 of fifth metatarsal ; nav. navicular ; tib. 

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

 fibula. 



