NO. 1976. TREESHREW8: FAMILY TUPAIID^—LYON. 159 



Genus PTILOCERCUS Gray. 



1848. Piilocercus Gray, Proc. Zool. Soc. London, 1848, p. 23. 



1864. Ptilocerus, Brehm, 111. Thierl., vol. 1, pp. 663-665. A misspelling of 



Ptilocercus. 

 1876. Ptilocerus, Wallace, Geographical Distribution of Animals, vol. 1, p. 337. 



A misspelling of Ptilocercus. 



Type. — Ptilocercus lowii Gray,^ the only species included in the 

 genus. 



Diagnosis. — An aberrant member of the family Tupaiidse, form- 

 ing the subfamily Ptilocercmse, distinguished externally by its large 

 thin ears, naked tail basally, distichously tufted distally, cranially 

 by absence of supraorbital foramen, and approximately parallel 

 temporal ridges; dentally by the relatively larger size of the first 

 upper incisors over the second pair, double-rooted upper canine, 

 without conspicuous diastema between second upper incisor and 

 upper canine, and absence of mesostyles on upper molars. 



External characters. — Ptilocercus differs very strildngly from any 

 other members of the family Tupaiidce m the form of its tail, which is 

 naked and scaly for about its proximal half or a little more, and dis- 

 tichously tufted for a trifle less than the distal half. The extreme 

 basal eighth of the tail is covered with soft furry hair like the adja- 

 cent parts of the body. Each scale of the naked portion of the tail 

 is subtended by tliree short hairs about equal to a scale and a quarter 

 or a scale and a half in length. The hands and feet of Ptilocercus are 

 relatively larger than in the other genera of the family, and the foot- 

 pads relatively larger, with an appearance of greater softness. The 

 fifth finger is as large as the second, and relatively much larger than 

 it is in Tupaia. The four interdigital pads are larger and more 

 rounded; the thenar and hypothenar are relatively larger and sit- 

 uated at about the same anteroposterior level; posteriorly the two 

 pads are connected by a slight bridge. Of the toes, the third, fourth, 

 and fifth are equal and the second nearly as large. The first toe is 

 well developed but much shorter than the others. Of the pads of 

 hind foot, the interdigitals are large and rounded; the small pad 

 accessory to the fourth interdigital is wanting. Corresponding to 

 the relatively shorter foot the proximal external pad is relatively 

 shorter than in Tupaia, and the proximal internal is much shorter 

 and wider and perfectly distinct from the fii'st mterdigital pad. 

 Mammae, 2-2=4. 



The ear of Ptilocercus is large, thin, and membranaceous in con- 

 trast to the small thick ear of Tupaia, with a fairly well developed 

 tragus and a ridgehk© antitragus. Viewed by the unaided eye, 

 both inside and outside of the ear is essentially naked, but under a 

 glass a few scattered hairs are found interiorly, and slightly more 



1 Proc. Zool. Soc. London, 1S4S, p. 23. 



