Abstract: In this paper material from 15 loealities is diseussed. 37 teeth were collected from the Guangsi Zhuang Autonomous Region of China during explorations under the leadership of professor Pei Wencheng in 1956-1957, and 5 of them were provided by Han Defen from Ling-yan cave. Liujiang County, Guangxi. 20 teeth, collected from a medicinal supply company,came from unnamed cave sites.
There is only one upper premolar.It has two cusps.There is a well-developed cingulum which runs from lingual aspect to the distal and buceal aspects of the tooth.
There are 30 upper molar specimens, of which 25 are either M1 or M2,5 are M3.For M1 or M2 each has four cusps; the paracone and metacone are highest. followed by the protoeone and hypoeone. In M3 the hypocone is less-developed. In some of the upper molars a well-developed lingual cingulum is expressed on the lingual aspect of the protocone. The size of some specimens which possess cingulum is large, a notch and a ridge are also present on their mesial border. The other teeth possessing cingulum are small and the noteh and ridge are lacking. It is possible that the former are of M2 and the latter are of M1.The cingulum on three specimens of M1 or Ma is not seen and the size of these teeth are smaller than those having cingulum.
The lower molars possess five cusps:a lypoconulid is added to each molar and it is positioned eentrally. The protoeonid and metaeonid are connected by a eotoeristid. The trigonid basin is narrower than the talonid.
Frisch (1965) documented that Hylobates concolor is distinguished by well-developed cingulum on the lingual aspect of the upper molars. I therefore deduced that the teeth possessing cingulum, which came from Guangxi, can be attributed to Hylobates concolor. In addition to the black gibbon two extant specics of gibbon(H.lar,H. hoolock) still exist in China. Those teeth without cingulum are possibly attributable to either H. lar or H. hoolock. The teeth of H.lar are smaller than those without cingulum found in Guangxi. As the distribution of this species is limited in our country,it is thought that these teeth with no cingulum possibly cannot belong to H.lar. No trace of cingulum could be found in nearly the total H. hoolock specimens, consequently,I regard those teeth without eingulum found in Guangxi as H. hoolock at present.
The chronologic distribution of the gibbon in China can be divided into three periods: Recent, Historie (400 B. Y.) and Pleistocene. Historical accounts (Gao Yaoting et al., 1981) and fossil evidenee show that the gibbon once ranged widely in China up to 31°N latitude. More recently, it reachs only to 26°N (see fig.5).
Cingulum is considered to be a primitive character. Moreover, a difference in the number of chromosomes exists between the three species of extant gibbon in China.The chromosome number in 94% of black gibbons (H. concolor) is 2n=52; in the others(H. lar, H. hoolock) 2n=44 in more than 90% of individuals,H. concolor may therefore be a more conservative animal than the other two species.
The evolution of the gibbon is still an open question. Recently, new material has been continuously found in China. Since Neogene times the vegetation has been favourable for the gibbon to live. It is possible that the ancestor of the gibbon may be found in China.

Key words: Gibbon; Pleistocene; China