34 o INSECTIVORES. 



THE TENRECS. 

 Family CENTETID^. 



With the curious-looking animal represented in the figure on the next page, 

 we reach the first member of a group of Insectivores, comprising four families, 

 which differ from all those yet noticed in the characters of their upper molar teeth. 

 In all the preceding families the upper molar teeth have broad crowns, with their 

 cusps arranged somewhat in the form of the letter W. On the other hand, in 

 all those remaining for consideration, the crowns of these teeth are narrow, and 

 carry on their crowns only three cusps, arranged in the form of 

 the letter V. These cusps, or tubercles, thus form a triangle, with 

 the apex directed inwardly ; and this type of molar tooth, of which 

 an example is represented in the accompanying illustration, is 

 consequently known as the tritubercular. It may seem that such 

 CROWN-SURFACE OF a point of distinction is of comparatively slight importance. Such, 



AN UPPER MOLAR .. . 1 . . i r i 



OFTHETRITUBER- however, is by no means the case, since the researches of palaeon- 

 CULAR TYPE. tologists have shown that nearly all the earlier Mammals had these 

 tritubercular molar teeth, from which we infer that Mammals still 

 retaining them in their primitive form belong to an extremely ancient stock. 



From this and other structural peculiarities it may be taken as certain that 

 the Insectivores of the present and three following families belong to a much lower 

 type of organisation than those already mentioned. And this is borne out in a 

 remarkable manner by their geographical distribution. Africa, and more especially 

 Madagascar, are characterised by the number of Mammals belonging to ancient and 

 primitive types still living there, as is well exemplified by the host of lemurs 

 found in Madagascar. Now of the Insectivores with tritubercular molar teeth, 

 the present and largest family is restricted to Madagascar and a few of the 

 neighbouring islands ; a second is found both in Madagascar and Africa ; the third 

 is solely African ; while the fourth is confined to the West Indies a region also 

 peculiar for the ancient types of its few Mammals. The whole of the tenrecs. 

 which as already mentioned are confined to Madagascar and a few small islands in 

 the vicinity, are characterised by their long skulls, which are not constricted 

 between the eyes, and have no zygomatic arch below the socket for the eye to 

 connect the upper jaw with the region of the ear, while the so-called tympanic 

 bulla is in the form of a simple ring. 



THE COMMON TENREC. 

 Genus Centetes. 



This animal, which is the one represented in the illustration on p. 341, is 

 readily recognised by its comparatively large size, and the total absence of a tail. 

 It is the sole representative of its genus, and, from the feature last mentioned, is 

 technically known by the name of Centetes ecaudatus. Adult males attain a length 

 of upwards of 16 inches, and are thus the largest of all Insectivores. The body is 



