THE FLYING-SQUIRRELS OF ASIA AND AFRICA 239 



tooth-structure obtains in most of the flying-squirrels of 

 Europe and Asia, although in the species shown in the 

 plate the structure has become somewhat more complicated 

 owing to the taller crowns of these teeth. In the scale-tails, 

 on the other hand, a totally different type of tooth-structure 

 obtains, the crowns of the molars being divided by trans- 

 verse folds of enamel, after a fashion recalling that which 

 prevails in certain South American rodents. 



To the anatomist these differences are sufficient to render 

 it quite certain that the scale-tailed flying-squirrels are, at 

 most, but very remotely connected with their non-scaled 

 namesakes of the northern hemisphere. The non-scientific 

 person might, however, say that the " yard-arm " in the 

 parachute and the scales on the tail are features which 

 have been developed concomitantly with the acquisition of 

 the parachute itself in certain species of flying-squirrels, 

 and that, like the differences in the structure of the teeth, 

 they are of no particular importance one way or the other 

 in regard to the affinities of the animals in which they 

 occur. 



A few years ago it would have been impossible to 

 produce absolutely decisive evidence as to the futility of 

 such specious arguments. Recently, however, there has 

 been discovered on the West Coast of Africa that home 

 of strange and primitive types of animal life a rodent 

 looking not unlike a large dormouse, which is really the 

 "grandfather" of all the flying scale-tails. For this creature 

 (known as Zenkerella), although without a parachute, has 

 scales on its tail like Anomalurus, and teeth of the same 

 type as the latter. Whether it is the actual form from 

 which the flying scale-tails are descended, or whether it 

 is itself a descendant of such ancestral form, may be left 

 an open question, as it is one of no practical importance. 



