PTEROMID^. 



Genus Ptbromts, Cuvier. 



Pteromts. 



Baron G. Cuvier^ was the first to separate the flying from the ordinary squirrels, 

 under the genus Pteromys. No one will be found to dispute the correctness of this 

 course, but while some naturalists have followed in the footsteps of Frederic Cuvier^ 

 in sub-dividing the flying squirrels into two groups, one Pteromys and the other 

 Sciiiropterus, others have failed to appreciate the significance of the characters 

 wliich he assigned to the genus Sciuropterus. 



As is weU known, E. Cuvier relegated to the genus Sciuroptems all the small 

 flying squirrels which he considered to resemble the ordinary squirrels by the con- 

 formation of their teeth, in the less complex character of the folds of enamel in 

 the molar series. 



I have examined the dentition in the following species, viz. : P. teromys oral, 

 P. caniceps, P. leucogenys, P. magnljiGus, P. melanotis, P. nitidiis, P. pimctatus, 

 P. tepliromelas, P. alhoniger, P. ftiscocapilhis, and P. volcms, — that is, in flying 

 squirrels belonging to both of the two supposed genera ; but, according to my obser- 

 vations, the form of the enamel folds in youth are essentially similar, consisting of a 

 series of tubercular folds which are marked with wavy lines in some, and are smooth 

 in others, but, in all, there is a mai^ked conformity to a common type. The seem- 

 ingly more complex character of the folds appears to depend on the extent to 

 which the tubercular ridges are worn by use. 



Since P. Cuvier wrote, many naturalists have been inclined to regard the dis- 

 tichous arrangement of the hairs of the tail, wliich is undoubtedly characteristic 

 of some species, as a feature common to all the smaller flying squirrels, or to those 

 which they have been wont to consider as belonging to the genus or sub-genus 

 Scmropten(,s ; but, after a careful examination of this organ, in nearly all the members 

 of the series, I have failed to detect that it is essentially distinctive of them — that 

 is, that the distichous arrangement of the hairs is always associated with a diminutive 

 species ; but, at the same time, there can be no doubt that it is more prevalent among 

 such. The tail is bushy in the following species, viz. : P. oral, P. cineraceus, 



1 Tab. Element, 1797, p. 135 ; Anat. Comp. 1799, vol. i. Tab. i. 

 3 Des Dent, des Mammif. 1825, p. 165. 



