xm PHYLUM CHORDATA 535 



developed in co-ordination with the great size of the pectoral 

 muscles. The sternal ribs are ossified. 



The scapula is large and oval in shape : the spine is near the 

 anterior margin : the post-scapula fossa has ridges for the origin of 

 the muscular fibres : the spine has a well-developed acromion. 

 The coracoid is elongated and in some cases bifurcated. The 

 clavicle is long. The pro-coracoid is represented by a separate 

 ossification ; there are rudiments of the sternal end of the coracoid 

 between the clavicle and the first rib. The humerus and radius are 



FIG. 1187. Skull of Pteropus fuscus. (After Blainville.) 



both elongated. The ulna is reduced, and is sometimes only repre- 

 sented by the proximal end, ankylosed with the radius. A large 

 sesamoid is developed in the tendon of the triceps muscle near 

 the olecranon process of the ulna. In the carpus the scaphoid and 

 lunar are united : sometimes also the cuneiform is united with 

 these : the pisiform is small. There is no centrale. The ungual 

 phalanges are absent in the nailless digits. The pelvis is small, and 

 the symphysis pubis often imperfect. The fibula is sometimes 

 well-developed, sometimes rudimentary. The tuber calcanei is 

 an inwardly curved process of the calcaneum, attached to which 

 by means of ligamentous fibres is a slender rod of bone or cartilage, 

 the calcar, which supports the inter-femoral membrane. 



Skeleton of the Primates. The atlas is ring-like, the 

 odontoid sub-conical. The spines of the cervical vertebrae are 

 usually well-developed and simple : in Man they are short with 

 the exception of the seventh and bifid : in some they are trifid. 

 The number of thoraco-lumbar vertebrae is usually nineteen, but 

 only seventeen in Man, the Gorilla and Chimpanzee, sixteen in 

 the Orang ; in some Lemurs it may be twenty-three or twenty-four. 

 The number of sacral vertebrae varies from two to five. The sacral 

 region of Man, which comprises five ankylosed vertebrae, differs 

 from that of other Primates in its greater relative breadth and in its 



