340 INSECTIVORES. 
THE TENRECS. 
Family CENTETIDA. 
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 shght importance. Such, 
oi Saat a however, is by no means the case, since the researches of paleeon- 
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 
