176 SYMPHALANGUS 



GENUS II. SYMPHALANGUS. THE SIAMANGS. 



, 2—8 „ 1—1 n 2—2 », a-3 



1- 2=2? <-• i^; P- 2=2; M. 3^:3 = 32- 



SYMPHALANGUS Gloger, Hand u. Hilfsb. Naturgesch., I, 1841, pp. 

 XXVII, 34. Type Pithecus syndactylus Desmarest. 

 Syndactylus Boitard, Jard. Plantes, Paris, 1842, p. 55. 

 Siamanga Gray, List Spec. Mamm. Brit. Mus., 1843, pp. XVII, 1. 



Size large ; skin of throat distensible overlying the large laryngeal 

 sac, which is formed by the extension of the thyrohyoid membrane. 

 Second and middle toes united by web as far as last joint. Skull large, 

 supraorbital ridges more developed than in Hylobates ; occipital 

 region more truncate. Frontal lobes of brain flattened ; olfactory bulbs 

 extend forward beyond frontal lobes of the cerebrum ; occipital lobes 

 small ; cerebellum projects from below the cerebrum backwards. 



LITERATURE OF THE SPECIES AND SUBSPECIES. 



1820. Desmarest, Mammalogie. 



SYMPHALANGUS SYNDACTYLUS described as Pithecus syndac- 

 tylus. 



1903. Miller, (G. S. Jr.), in Smithsonian Miscellaneous Collections. 

 SYMPHALANGUS KLOSSi first described. 



1908. Thomas, in Annals and Magazine of Natural History. 

 Symphalangus syndactylus continentis first described. 



GEOGRAPHICAL DISTRIBUTION OF THE SPECIES AND SUBSPECIES. 



Sumatra contains S. syndactylus, and 5". J. continentis is found 

 in the Malay Peninsula possibly as far north as Tenasserim. South 

 Pagi Island off the west coast of Sumatra has 6". klossi. 



KEY TO THE SPECIES AND SUBSPECIES. 



A. With laryngeal sac. Color all black. 



a. Size very large S. syndactylus. 



b. Size smaller 6". j. continentis. 



c. Size very small 5. klossi. 



