PEIMATES FEOM MADAGASCAE. 



145 



of twenty-seven pelves. 



to name some genus or species of Monkey where a similar character occurs. Should 

 such examples prove to be chiefly drawn from one or two families, the presumption 

 will be strong that they are not mere examples of convergence, but point to community 

 of origin (see text-fig. 48, p. 152). 



To begin, then, our comparative survey : — 



TJie Brain. — A comparison of the various subfossil Malagasy Lemurs reveals one 

 feature which is common to all of them without exception, and which has therefore 

 been repeatedly referred to in the previous descriptive sections, namely, the curious 

 narrowing of the frontal region of the skull immediately behind the orbits. The 

 annexed figure (text-fig. 40) shows the outlines of these various skulls all reduced to 

 a common unit length for convenience of comparison. Examples of the nearest 

 extant genera and the skull of a New World Monkey are also appended. 



If it is asked what has caused this curious narrowing of this region of the skull, 

 it is only possible to offer one or two suggestions. It is noteworthy that it is in 

 all the extinct forms that this peculiarity is most marked. Dr. Elliot Smith points 

 out in his report on the brain-casts of Mesopro^pithecus, Palceopropithecus, and Lemur 

 majori, which is published simultaneously with this memoir, that it is the frontal lobes 

 of the brain which are the latest to be evolved, and it is this region which is the 

 first to go when retrogressive evolution occurs. May not the loss of intelligence 

 which this degeneracy connotes be among the causes of the disappearance of these 

 forms % It is also perhaps not a mere coincidence that these forms all have relatively 

 more massive mandibles than the extant genera. The presence in nearly every case 

 of a sagittal crest and widely curved zygomata implies the possession of powerful 

 temporal muscles. Is it not possible that the mechanical pressure of these muscles 



