64 THE GENERAL ANATOMY OF THE LEMUROIDEA [SECT. A 



and diurnal groups : omnivorous and herbivorous forms : some 

 types hibernate, though these are exceptional. The numbers of 

 teeth and of the carpal bones are not absolutely constant through- 

 out the Sub-order. 



But although such diversity of form and habits must not be 

 overlooked, it is still true that a large number of Lemurs agree in 

 certain general characters. Such a group may fairly be called 

 typical, and from it the present selection must be made. It is 

 perhaps noteworthy that the very fact of such variability is of 

 itself suggestive that the Sub-order provides materials from which, 

 in the course of Evolution, higher types may be reasonably 

 supposed to have arisen whether through Natural Selection or 

 otherwise. At the same time, it is not necessary to suppose that 

 the "true Lemurs" represent exactly the particular varieties thus 

 favoured and consequently figuring in the ancestral history of the 

 higher Primates. Indeed the opinion has been expressed (Forsyth- 

 Major, Standing) that so far from advancing, many of the existing 

 types have degenerated, from more highly-organised ancestors. 

 However this may be, the choice of an example for descriptive 

 purposes will fall advisedly on a specimen of the so-called " true " 

 or typical Lemurs, which is described in the following paragraphs. 



I. General considerations. 



In the morphological study of the Lemurs, attention must be 

 directed to the facts (i) that they constitute a relatively primitive 

 group of Eutherian mammals, (ii) that they are quadrupedal, 

 (iii) that they are arboreal and nocturnal in habit, (iv) that they 

 are in diet usually insectivorous or omnivorous. It is probable 

 that in reference to these considerations will be found the inter- 

 pretation of all their salient structural characters. These will 

 be found arranged in sequence either according to the various 

 anatomical systems described, or in certain instances with refer- 

 ence to regions of the body. 



II. Systematic description. 



A. External characters. The commonest type of Lemur 

 resembles in size a cat, and, as in that animal, the tail is long 

 (Fig. 17). To its relatively small size and also to its nocturnal 



