490 



ZOOLOGY 



SECT. 



develop vertical laminae and form no palatine plates. The ascend- 

 ing ramus and coronoid process of the mandible are both well 

 developed. 



In the American Anteaters and Armadillos, the bones of the 

 fore-limb are short and powerful. The scapula in the Anteaters 

 is broad and rounded ; the anterior border unites with the coracoid 

 process so as to convert the coraco-scapular notch into a foramen. 

 In the middle of the spine there is a triangular process : a ridge on 

 the infra-spinous fossa presents the appearance of a second spine. 

 The fibres of origin of the subscapularis muscle extend on to the 

 outer surface as far forward as this ridge, so that the part of the 

 outer surface behind the ridge corresponds to a part of the 

 subscapular fossa, which in other Theria is co-extensive with the 

 inner surface. Except in Cydoturus the clavicles are rudimentary. 

 All the carpal bones are distinct. 



In the Armadillos the scapula (Fig. 1072) has an extremely 

 prolonged acromion (acr.\ sometimes articulating with the humerus 



The ridge (sp'.) representing a second 

 spine is present. The clavicle is 

 well developed. The humerus is short 

 and powerful with well developed 

 processes and ridges, and with a 

 foramen above the inner condyle 

 (entepicondylar foramen}. The carpus 

 consists of the ordinary eight bones. 



In the Sloths (Fig. 1073) the 

 bones are comparatively long and 

 slender. A coraco-scapular foramen 

 is formed as in the Anteaters. In 

 the three-toed Sloths (Fig. 1074) 

 the acromion (acr.) is at first con- 

 nected with the coracoid process, 

 but becomes reduced and loses the 

 connection; in the two-toed Sloth 

 the connection persists. The clavicle 

 (cl.) is not directly connected inter- 

 nally with the sternum ; externally it 

 is connected with the coracoid process 

 -a condition observed in no other 



Mammal. The humerus is very long and slender, so are the 

 radius and ulna, which are capable of a certain amount of move- 

 ment in pronation and supination. In the carpus (Fig. 1075) 

 the trapezoid and magnum are united in Bradypus, distinct in 

 Cholcepus : in the former the trapezium is usually fused with the 

 rudimentary first metacarpal. The first and fifth metacarpals are 

 represented only by rudiments. The proximal phalanges of the 

 three digits are early ankylosed with the corresponding meta- 



Fin. 1072. Shoulder-girdle of Arma- 

 dillo (Dasypus sexcinctus). acr. 

 acromion ; cor. coracoid process ; 

 in-. 8C. pre-spinous fossa ; pt.sc. post 

 spinous fossa ; sp. spine ; sp'. ridge 

 probably marking the anterior 

 limit of origin of the subscapularis 

 muscle. 



