240 MOSTLY MAMMALS 



But it may be taken as certain that the flying scale-tails 

 of which, by the way, there are two distinct generic types 

 (Anomalurus and Idiurus) are the specialised descendants 

 of a creature closely allied to, if not identical with, Zenkerella. 

 It may further be affirmed with certainty that the evolution 

 of the flying from the non-flying scale-tails has taken place 

 in Africa. Whether, however, Zenkerella itself is an aborigi- 

 nal African type, or an immigrant into the dark continent 

 from the north, is a question difficult to answer at the 

 present time. 



Although the flying-squirrels of Europe and Asia have 

 been known from time immemorial, their pedigree is not 

 so easy to trace as is that of the scale-tails. Probably 

 they were evolved from non-flying squirrels at an earlier 

 date than that at which Anomalurus branched off from 

 Zenkerella (or its prototype), as they appear to be repre- 

 sented by teeth in some of the earlier Tertiary deposits 

 of Europe. It is therefore quite probable that even the 

 generic types from which they trace their descent have 

 died out. Nevertheless, it may be considered practically 

 certain that they are descended from rodents more or less 

 nearly allied to the true squirrels of the genus Sciurus. 

 Their pedigree is therefore wholly distinct from that of their 

 reputed cousins, the scale-tailed flying-squirrels of Equatorial 

 Africa. 



In appearance the true flying-squirrels, of which there 

 are three distinct generic types, are very similar to 

 ordinary squirrels, as indeed they are in their habits ; 

 their long flying leaps, during which they half float in the 

 air by the aid of the parachute, being only an extension 

 of the bounds taken by the ordinary red squirrel in its 

 passage from tree to tree. Many of them are even more 

 beautifully coloured than ordinary squirrels. Compared 



