cüscüs. 89 



hindmost molars. lu our large series of skulls belonging 

 to mounted specimens of all ages this process is to demon- 

 strate on the most decisive way. Some specimens become 

 the dentition complete at a very advanced age and attain 

 a larger size than other specimens ; our although large 

 collection is however too small to decide whether these 

 differences are constant to certain localities (islands) or are 

 caused by the influence of temperature or food and inde- 

 pendent from locality. The different degrees of develop- 

 ment of the occipital crest have seduced some authors to 

 regard not fullgrown specimens as distinct species. 



Passing over the shape of the nasalia , which is con- 

 stantly distinct in the different species , and other osteo- 

 logical details I will fix the attention upon the premolars 

 as they show some particularities , especially in the speci- 

 mens of Cuscus orientalis and Cuscus maculatus. discus 

 orientalis has three (of which one small) premolars in each 

 upper-, and four (of which three small) in each lower jaw , 

 meanwhile Cuscus maculatus wants the midmost (the small) 

 upper premolar and has three lower premolars (of which 

 two small). There are in the named two species several 

 abnormalities as to the number of the small premolars, 

 so that although there are no differences in the form of 

 the skull or in the shape or number of the other teeth , 

 some specimens have one or more small premolars too less 

 or too much. This fact has been observed by Waterhouse , 

 Gray , Alston and other naturalists , but it was impossible 

 to decide what was the normal number and what abnor- 

 mal , because they had no large series at their disposal. 

 Among our number of sixty skulls of Cuscus orientalis I 

 find a number of seventeen , which present abnormalities 

 in the dentition: four have no trace of midmost upper 

 premolar, viz: N». 121 (skull of N». 57), N". 138 (skull 

 of N^ 79), N'^. 141 fskull of N". 82) and N». 142 (skull of 

 N<^. 83); two have no midmost left upper premolar, viz: 

 W. 137 (skull of N«. 78) and N". 143 (skull of No. 84); 

 one has no midmost right upper premolar , viz : N". 147 



Notes from tlie Leyden ÜVLuseuin, 'Vol. VII, 



