TENRECS. 43 



W-like manner, in the former these teeth are triangular, 

 with their cusps arranged in a V. There are five 

 species of tenrecs, classed under three generic headings, 

 and all characterized by the absence or small size of the 

 tail. The largest, and at the same time the most generalized 

 of all, is the common tenrec (Centetes ecaudcdus\ which 

 attains a length of from twelve to sixteen inches, and is 

 characterized by the absence of a tail, by the rows of spines 

 on the back being shed in the adult state, and also by 

 certain peculiar features in the dentition which appear to 

 indicate relationship with the pouched mammals. The 

 spiny tenrecs ( ffemicentetes) are much smaller animals, of 

 the size of moles, in which the longitudinal rows of spines 

 on the back are retained throughout life. They have the 

 same number of teeth as fully adult individuals of the 

 common tenrec ; but whereas in the latter there are four 

 upper molars and two upper incisors, in the spiny tenrecs 

 there are three of each of these teeth. In the loss of the 

 last molar these tenrecs are evidently more specialized 

 than the common species, but the presence of the third 

 incisor shows that they are descended from a still more 

 generalized type. Lastly, we have the hedgehog-tenrecs 

 (Ericulus). in which the whole upper surface of the body, 

 as well as the short tail, is thickly beset with spines, 

 thus giving the hedgehog-like appearance from which the 

 creatures derive their name. The dentition is more reduced 

 than in either of the upper groups, thus indicating the 

 greater specialization of the genus ; although the presence 

 of a short tail indicates direct descent from a tailed 

 ancestor. Although it is quite clear that the three genera 

 of tenrecs are divergent branches from a common stock, 

 yet it is not impossible that they may indicate the 

 manner in which the complete coat of spines characterizing 

 the third group has been gradually evolved. Against this 

 view it may, however, be urged that if the common tenrec 

 indicated the first commencement of the spiny coat, it 

 would be more likely to find the spines in the adult rather 

 than in the young. Be this as it may, the wide difference 

 between the hedgehogs and the tenrecs, coupled with the 

 affinity of the former to the gymnuras, leaves no doubt 



