112 On a new Gibbon Jrom Annam, 



These suggestions about the homologies are of necessity 

 only provisional, and are quite likely to be modified when a 

 microscopical study of embryonic specimens of the group 

 indicates with certainty which teeth have rudimentary milk- 

 predecessors, no functional milk-teeth having as yet been 

 observed. 



XIII. — A new Gibbon from Annam. 

 By Oldfield Thomas. 



(Published by permission of the Trustees of the British Museum.) 



Among the collections which have been obtained in recent 

 years in Annam by Dr. and Mrs. Vassal there occurs a 

 Gibbon which appears to be quite distinct from any pre- 

 viously described. I propose to name it in honour of 

 Mrs. Vassal, to whose help much of her husband's success iu 

 obtaining interesting animals has been due. 



IJylobates gabnellce, sp. n. 



A black species without light frontal band, but with a 

 conspicuous buffy gular patch. 



General colour as in H. leucogenys, Ogilb.*, tlie ground- 

 colour similarly deep black, but instead of the light- throat 

 and \\hisker-mark being white and extending up on each 

 side to the level of the eyes, it is deep yellowish buffy and 

 barely rises on eacli side above the angle of the mouth. Its 

 hairs are soft and woolly, instead of being so stiff as to form 

 a definite outstanding fringe ; it is broader below, and, passing 

 under the throat, entirely isolates the black chin from the 

 black of the cheeks and chest. 



Skull larger than that of H, agilis, H. lar, and other 

 Gibbons in the Museum Collection, which, however, does not 

 contain tlie skull of B. leucogenys. In fact the skull of 

 H. gabriellcB is almost as large as that of a Siamang. In 

 shape it is most like that of H. leuciscus, but the temporal 

 constriction is deeper and the orbits more outstanding. 



SkuU-dimtnsions (those of the skin being of no value) : — 



Greatest length 116 mm.; basal length 83; zygomatic 

 breadth 76 ; breadth across outside orbits 66"5 ; breadth of 



* Figured by Sclater, P. Z. S. 1877, p. 680, pi. Ixx. 



