162 PROCEEDTNOS OF THE NATIONAL BIUSEUM. vol.45. 



Dental characters. — There are not so many fundamental differences 

 between the teeth of Ptilocercus and Tupaia as there are between 

 the skulls, perhaps no more than generic differences. The upper 

 canine is distinctly two-rooted and premolariform in shape. At 

 times the upper canine in Tupaia is also two-rooted, but is not 

 premolariform in shape. The first upper incisors are very much 

 larger than the second pair, usually disproportionately more so than 

 is usual in Tupaia. Both pairs of upper incisors are somewhat differ- 

 ently shaped in Ptilocercus and Tupaia. In the latter they are simple 

 cone-like recurved teeth ; in Ptilocercus these teeth are more trenchant 

 with a moderately well-developed posterior cuttmg edge, and the 

 second incisor almost has a distinct posterior cusp. Owing to the 

 shortness of the rostrum, the incisor-canine-premolar series of teeth 

 stand closer in tke tooth row than they do in Tupaiinse. The second 

 upper premolar is three-rooted, as is usually the case in Tupaiinee, 

 and also is more triangular and more like the last upper premolar in 

 shape. The last upper molar is more compressed antero-posteriorly 

 in Ptilocercus than in Tupaia. The upper molars of Ptilocercus lack 

 the mesostyle, which is quite conspicuous in Tupaiinse; the cusps on 

 the teeth appear blunter and more rounded. The molars are sur- 

 rounded by a distinct cmgulum, absent in Tupaia. In the lower jaw 

 the first and third incisors are relatively smaller with respect to the 

 second incisor in Ptilocercus than in Tupaia. The lower canines are 

 about the same relative sizes in the two genera, but in Ptilocercus 

 they are less canine-like in shape and look like enlarged first pre- 

 molars. In Ptilocercus the middle lower premolar is much smaller 

 than either of the two other premolars and is below the general level of 

 the lower tooth row, while in Tupaia it is the first which is the 

 smallest of the premolar series and which stands below the level of 

 the tooth row. The lower molar teeth have a well-defined cingu- 

 lum on their outer aspect, lacking in Tupaiinae, but otherwise no 

 essential differences are found in the two genera. See figure 15, 

 page 161. 



Geograpliic distrihution . — Ptilocercus is found in Borneo, Banka, 

 Sumatra, and Pulo Pinie of the Batu Islands, and in the southern 

 part of the Malay Peninsula. It is said to exist on Sirhassen of the 

 Natuna Islands.' See Nos. 2 and 3 on map, page 133. 



Nuonber of forms. — Ptilocercus contains but a single species group, 

 loivii, of which one geographic race has been described. 



RemarJcs. — Ptilocercus differs in external and particularly in cran- 

 ical characters from any of the other genera of the Tupaiid.-ic more 

 than any of them differs from each other, and seems well worthy of 

 subfamily rank. The most striking differences are found in the ears, 

 tail, feet, supraorbital foramen, and certain foramina at base of skull, 



I See Thomas and Hartert, Nov. Zool., vol. 1, p. 656, September, 1894. 



