The Common Mole occurs not only in the British Islands, but across the whole of the central and southern parts of the continent of Europe, extending northwards as far as the southern shore of the Baltic and throughout Denmark, thus justifying Shakspere’s allusion to it in “Hamlet.” It also stretches across Central Asia to the confines of China, and according to some writers extends through Persia into India. It is subject to much variation, which may be due to differences of soil or climate. Thus Mr. Bell records Moles “of a deep black colour, of a mouse-grey, dark olive-brown, pied, yellowish-white, and wholly or partially orange;” and mentions specimens from Berne “of the usual dark-colour, but having a well-defined lozenge-shaped patch of orange on the breast.”
DENTITION OF COMMON MOLE.
The Common Mole is the type of the restricted genus Talpa, the species of which are entirely confined to Europe and Asia. In these animals the elongated muzzle projects considerably beyond the opening of the mouth, and contains a pair of long tubular nostrils; it is supported by cartilage, and further strengthened by a small bone at the extreme tip. The teeth with which the jaws are armed are of formidable character, and plainly indicate the predaceous habits of the animal. There are always three true molars on each side in each jaw, and these are armed with several strong points united by ridges, but the number of the other teeth is slightly variable (the total number of teeth ranging between forty and forty-four), and even the determination of their precise nature is somewhat obscure. The dentition of the Common Mole (see [figure]) is now, however, generally regarded as follows: In the upper jaw, on each side, three incisors, one large canine provided with two roots, and four premolars, of which the hindmost is of large size; in the lower jaw, on each side, four incisor-like teeth, the hindmost of which is probably a canine, and four premolars, the foremost of which is very like a canine. The variation in number is caused by the absence of some of the premolars and incisors of the lower jaw.
FORE-LIMBS OF COMMON MOLE.
The structure of the fore-limbs, and the bones supporting them, in the Mole and its allies, is not only to be regarded as their most distinctive character, but also as furnishing a most striking example of the adaptation of means to ends. The Moles are condemned to live almost constantly underground, and their very existence depends on the facility with which they can make their way through the earth. The fore-feet, by means of which they dig, are accordingly converted into strong, broad, shovel-like organs, armed with broad, flat claws. The five toes of which these feet are composed consist each of two short joints and a long one, the latter making nearly half the length of the organ; and these long joints, which support the claws, are cleft at the tip and grooved underneath to receive an internal process of the nail, which serves to add to its strength and firmness. The bones of the wrist are short and firmly packed together, and from the scaphoid bone springs a long curved falciform bone (f [in figure]), which runs from the wrist to the first toe, which it helps materially to stiffen and support. The arm which supports this powerful hand is also of peculiar construction. In the forearm (a) the radius and ulna are distinct, but the acromion (or elbow) process of the latter is very long, and widened at the extremity, giving great power to the action of the limb. The humerus (b) is quite different from anything to be met with elsewhere in the Mammalia, being a short and very stout bone, rendered most irregular in its outline by the development of great crests and processes. It not only articulates with the shoulder-blade, but has a separate surface for the reception of the extremity of the collar-bone (c), which is a short bone resembling the vertebra of a fish. The shoulder-blade (d) is long and narrow, but stout and triangular in its form.
STERNUM OF COMMON MOLE.
The sternum, or breast-bone, upon which all these parts rest, is scarcely less singular in its structure (see [figure]). The body of the sternum consists of four short pieces, which receive the ends of the ribs. Behind these is a slender ensiform process (e), and in front of them a manubrium (m), or presternum, of peculiar form, and quite as long as the whole middle part of the sternum. This part is widened in part of its length, receives a single pair of ribs in its hinder division, has a strong keel for the attachment of the pectoral muscles along its lower surface, and is much thickened at its front extremity, to the sides of which the collar-bones (c) are articulated. By this arrangement the whole fore-limb is thrown forward close to the head, and placed in the most favourable position for facilitating the burrowing operations of the animal, which are effected by bringing forward the fore-feet to the level of the nose, and then separating them and pushing backward, with an action that might almost be styled swimming through the ground. The hind feet, which are much smaller than those just described, are perfectly plantigrade in their structure. They also contain five toes, armed with small sharp claws, and are used only for the purpose of progression.