The Shrew Mole, which is often called simply the Mole in the United States, is another very widely-distributed species in North America, throughout the whole eastern part of which it is found abundantly. Like the other species of its genus, which inhabit the territories farther west, the Common Shrew Mole has an elongated, slender snout, which is cut off obliquely at the end, so that the nostrils, which are situated in this sloping surface, are turned forwards and upwards, and are not visible from below; a short and nearly naked tail; and only thirty-six teeth, which present the following characters:—In the upper jaw there are on each side three incisors, of which the foremost is very large and pyramidal, whilst the other two are very small; then four compressed teeth, gradually increasing in size, of which the first may be regarded as a canine and the rest as premolars; and beyond these three large, true molars, each having the crown furnished with strong cusps, and distinctly divided into two parts. The lower jaw has only four instead of six incisors, and these are nearly horizontal, and the two inner ones are much smaller than the outer; these are followed immediately by three simple, gradually increasing teeth, regarded as premolars; and these again by three large true molars. According to this interpretation there are no lower canines. The feet are like those of the Mole, but the toes of the hind feet are webbed.
Two other species of Scalops are found in the western parts of the United States. One of them, the Prairie Mole, or the Silvery Shrew Mole (S. argentatus), which is about seven inches long, and has the hairs annulated with white and lead colour, giving it a silvery appearance, inhabits the western prairies, advancing as far to the eastward as Ohio and Michigan; the other, the Texan Shrew Mole (S. latimanus), which is still larger, and has the fore feet broader than in any other species, and the black hair longer, thinner, and slightly crisped, is a native of Mexico and Texas.
Two other Shrew Moles have been formed into a distinct genus (Scapanus) by M. Pomel. They resemble the preceding in general characters, but agree with the Star-nosed Mole in having forty-four teeth. These are Brewer’s Shrew Mole (Scapanus Brewerii), a black species, about six inches long, which inhabits the eastern United States, and is supposed to have given the foundation for the reports of the existence of the Common Mole in North America; and the Oregon Mole (Scapanus Townsendii), a considerably larger species, which is said to extend all along the Pacific coast, from California to 47° 10′ N. lat. In their habits these animals seem to agree closely with the Star-nosed Mole. The western species occurs abundantly in the banks of rivers.
FAMILY IX.—MYOGALIDÆ.—THE DESMANS.
Some very curious and interesting animals, placed with the Shrews by some zoologists, and with the Moles by others, may, perhaps, for our purpose, be best placed as a distinct family. The Desmans are, in fact, Shrew-like animals, with some important points of resemblance to the Moles. Thus, the teeth in the true Desmans are forty-four in number, and the large upper front incisor is pyramidal, and rather resembles that of some Moles than that of the Shrews; the general character of the skull is Mole-like, especially the presence of a slender zygomatic arch, which does not exist in the Shrews; the shoulder-blade is long, narrow, and strong, the collar-bone short and stout, and the front portion of the sternum is slightly keeled. Many other slight osteological peculiarities point to an alliance with the Moles; but on the other hand, Shrew-like characters are not wanting, and the general structure of the body and limbs is that of the Shrews, the tail being well developed, and the limbs all formed for walking. In the true Desmans the hind limbs are considerably larger than the fore-limbs, and all the feet are palmated, or have their toes united by webs.
THE DESMAN.[277]
The Desman in general form resembles a big Rat, but with a long snout formed by the nostrils, which are produced in a tubular form, and united in the middle, producing a regular trunk, provided with muscles which enable it to be turned in various directions, and employed as an organ of touch. The tail is compressed, scaly, and nearly naked.
In the arrangement of the teeth we see a considerable resemblance to the Shrew Moles. Thus, in the upper jaw we have the same gigantic front incisors, larger here than in any other species, and these are followed on each side by a series of seven teeth, gradually increasing in size, the first of which is an incisor, the second a canine, and the remaining five premolars. In the lower jaw, there are four projecting incisors, the outer much larger than the inner ones, as in the Shrew Moles, then, on each side we have six gradually enlarging teeth, a canine, and five premolars. The true molars are three in number on each side in both jaws. They are broad, powerful teeth, with strong acute tubercles, and crowns divided transversely into two parts. The eyes are small, and there are no visible ears.
Another peculiarity of these animals is the presence, under the root of the tail, of a large gland, which secretes a substance of a strong musky odour, whence they are sometimes called Musk Shrews. This gland is composed of from twenty to forty lobes, each having a dilated upper part, and a narrow lower portion, and containing in their walls a great number of small secreting sacs.
