SUREIVS. 
323 
Extinct Gym- Extinct Insectivores, more or less closely allied to the gymnuras, 
nuras. have left their remains in the Tertiary deposits of France belonging 
to the upper portion of the Eocene and the lower part of the Miocene period. 
These extinct forms, although belonging to distinct genera from those now existing, 
serve to show the antiquity of this group of animals; and, in common with many 
others, further indicate how the early Tertiary fauna of Europe has its nearest 
representatives in the remote islands of the Malayan Archipelago. 
The Shrews. 
Family SomciDJE. 
The elegant little creatures known as shrews, or shrew-mice as they are often 
termed from their mouse-like form, constitute the fourth family of the true 
Insectivores. So like, indeed, are these animals to mice and rats, that in popular 
estimation they are often confounded with them; although they are readily 
distinguishable by their long and pointed snouts, their rounded ears, closely pressed 
to the sides of the head, and the characters of their teeth. 
Though there would be little likelihood of mistaking a shrew for a hedgehog, 
it is necessary to point out in some detail the characters on which naturalists 
refer these groups to separate families; since, as we have seen, the spines of the 
hedgehogs do not form a characteristic of more than generic importance. 
Perhaps the most ready means of determining whether or no an Insectivore 
belongs to the shrew family is afforded by the characters of the first pair of front 
or incisor teeth. In all shrews these teeth are different from the others; those 
of the upper jaw (as shown in the figure) being long and generally sickle-shaped, 
with a more or less distinct cusp at the base of their 
hinder border; while in the lower jaw they are long 
and project horizontally forwards, sometimes curving 
upwards at the tips. Moreover, with the single excep¬ 
tion of one peculiar African species, which has a rudi- 
mental seventh tooth, the lower jaw of every shrew has 
only six teeth on each side. 
The above features are sufficient to distinguish 
a shrew from any other Insectivore; but a few additional 
characteristics may also be mentioned. Thus the first 
and second upper molar teeth of all the shrews differ 
from those of the hedgehogs and gymnuras by the 
absence of the fifth or central cusp on the crown. 
Then, again, the skull of a hedgehog or gymnura, as 
shown in the figure of the skeleton of the former given on p. 308, has a complete 
bony bar—the zygomatic arch—running below the socket for the eye to connect 
the upper jaw with the hinder part of the skull. In a shrew, on the other hand, 
this bony arch, as shown in the accompanying figure, is invariably incomplete 
beneath the eye, owing to the absence of the cheek-bone. 1 A further char¬ 
acteristic feature of the shrews is the extreme length and narrowness oi their skulls. 
1 In one Indian liedgeliog the zygomatic arch is incomplete. 
SIDE VIEW OF THE EIGHT ANTERIOR 
UPPER TEETH OF THE SWIM¬ 
MING SHREW FROM UNALASKA 
ISLAND. 
Much enlarged. The first upper 
incisor (the tooth on the right of 
the figure) is less sickle-shaped 
than usual.—After Dobson. 
