The fifteenth order of Mammals is that of the Insectivora, comprising a number of small Mammals which are very similar to the Rodents in many respects, but want the peculiar incisors of that order, and are likewise almost always furnished with clavicles.

In the Insectivora, all the three kinds of teeth are usually present, but the exact nature of the dentition varies considerably in different cases. The incisors and canines present little special, but the molars (fig. 445) are always serrated with numerous small pointed eminences or cusps, adapted for crushing insects. With one exception (Potamogale), clavicles are always present in a complete form. All the feet are usually furnished with five toes ; all the toes are furnished with claws ; and the animal walks on the soles of the feet, or is plantigrade. The testes pass periodically from the abdomen into a temporary scrotum; and the placenta is deciduate and discoidal. They are mostly nocturnal and subterranean, and generally hibernate. They are all of small size, and are found everywhere, except in the continents of South America and Australia, where their place is filled by Marsupials.

The order Insectivora has been divided variously by different authorities, but the following are the principal families:

Fam. 1. Talpidae. - The body in this family is covered with hair; the feet are formed for digging and burrowing, and the toes are furnished with strong curved claws. There are no external ears; and the eyes in the adult are very small, or may be covered by the skin. The clavicles are strong, the arm very short, the hand wide, and the palm turned outwards and backwards. The fur is short and velvety, and the tail very short or wanting, in most cases.

The common Mole (Talpa Europaea, fig. 446) is the only

Fig. 445.   Dentition of the common Mole (Talpa Europaea).

Fig. 445. - Dentition of the common Mole (Talpa Europaea).

British species of the family, and is too well known to need any description. The dental formula of the Mole is:

i

3 - 3

; c

1 - 1

; pm

4 - 4

; m

3 - 3

=

44.

3 - 3

1 - 1

4 - 4

3 - 3

The nearly-allied Talpa caeca of Southern Europe has the eyes covered by a membrane, pierced by a small central aperture. Other species of Talpa are found in India, China, and Japan.

Fig. 446.   European Mole (Talpa Europaea).

Fig. 446. - European Mole (Talpa Europaea).

The star-nosed Moles (Condylura) are North American, and are distinguished by a fringe of elongated membranous caruncles surrounding the nostrils. The tail is much longer than in the typical Moles; the eyes are very minute; and there are no external ears.

Also North American is the genus Scalops, comprising the so-called Shrew-moles. In this genus the tail is short, the muzzle is long, with the' nostrils at its extremity, and the eyes are very small and are hidden in the fur. The common Shrew-mole (Scalops aquaticus) has the hind-feet webbed, and is found everywhere in the United States east of the Mississippi.

The Golden Moles (Chrysochloris) of South Africa are often regarded as forming a special family. They are like the Moles in form and general habit; but the hairs of the fur have the power of dispersing the rays of light, and thus of giving rise to beautiful metallic colours. The fore-feet have four toes, the second and third being very large and armed with immense claws; while the clavicles are not shortened (as they are in Talpa). The eyes are very minute, and covered by the skin. The dentition is quite peculiar, the dental formula being Lastly, in the curious genus Urotrichus (sometimes referred to the Myogalidae), of Japan and the north-west of America, the nose is long and cylindrical, terminated by a naked fleshy bulb, and extremely sensitive, the tail is moderately developed and hairy, and the fore-feet are adapted for burrowing. Allied forms have also been recently discovered in North China and Thibet.

i

3 - 3

; c

0 - 0

; pm

1 - 1

; m

6 - 6

or

5 - 5

=

36

or

40.

2 - 2

0 - 0

3 - 3

5 - 5

4 - 4

Fam. 2. Polamogalidae. - This family merely requires to be mentioned as founded for the reception of a single genus (Potamogale), comprising only a single species (P. velox). This animal is a curious Otter-like Insectivore, which leads a semi-aquatic life, to which end it has a long compressed tail. Clavicles are also entirely wanting. It is confined to the west of Africa.

Fam. 3. Soricidae. - The Soricidae or Shrew-mice are distinguished by having the body covered with hair, and the feet not adapted for digging; whilst there are mostly external ears, and the eyes are well developed. The tail is nearly naked, and scaly; the central upper and lower incisors are very large; the tibia and fibula are united; and there is no caecum. Of all the Insectivora, no division is more abundant or more widely distributed than that of the Shrew-mice, their range extending over North America and the whole of the Old World, In general form and appearance the Shrews very closely resemble the true Mice (Muridae) and the Dormice (Myoxidae), but they are in reality widely different, and must not be confounded with them. The Common Shrew (Sorex vulgaris), the Garden Shrew (Crocidura aranea), and the Water-Shrew (Crossopus fodiens) are well-known British species of this family. The smallest known Mammal is one of the Shrews (Sorex Etrus-cus), which is not more than two and a half inches in length, counting in the tail.

Ths Desmans or Musk-rats, forming the genus Myogale, are sometimes placed here, sometimes in the family of the Talpidae, and are often raised to the rank of a distinct family (Myogalidae). They have the nose prolonged into a kind of flexible proboscis, whilst the feet are webbed, and the tail is compressed, thus adapting the animal for a semi-aquatic life.

The dental formula is: