886 



PHYLUM CHORDATA : CLASS MAMMALIA 



directed downwards, those of the forearm upwards ; 

 except the plantigrade gibbons, the apes tend to walk on the 

 edges of their feet ; there are no cheek-pouches ; there 

 are no ischial callosities except in gibbons ; the caecum 

 has a vermiform appendix. 



f^ 



P 



I 



Fig. 521. — Skull of orang-utan. 

 p.. Parietal ; /., frontal ; sq., squamosal ; j., jugal; m., maxilla. 



The Gibbons (Hylobates) live in S.-E. Asia, especially in the Malayan 

 region. The largest attains a height of 3 ft. They walk erect with 

 the hands reaching the ground. The skull is not prolonged into a 

 vertical crest. There is an os centrale in the carpus. The hallux is 

 well developed. The only flat nails are those of poUex and hallux. 

 There are 13 ribs and 18 dorso-lumbar vertebrae. There are small 

 ischial callosities — the only instance in Anthropoids. They are mainly 



