SHRE WS. 



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 SORICIDJE. 



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- V. 



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. 



ml , P ^ . ,...., SIDE VIEW OF THE RIGHT ANTERIOR 



I he above teatures are sufficient to distinguish UPPER TEETH OF THE SWIM- 



a shrew from any other Insectivore ; but a few additional MING SHREW FROM UNALASKA 

 characteristics may also be mentioned. Thus the first 



and second upper molar teeth of all the shrews differ Much enlarged. The first upper 



,, fj-i-i-ii i iji incisor (the tooth on the right of 



from those of the hedgehogs and gymnuras by the the figure) is less sickle . sliaped 

 absence of the fifth or central cusp on the crown, than usual. After Dobson. 

 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 of their skulls. 



1 In one Indian hedgehog the zygomatic arch is incomplete. 



