The sternum offers some peculiarities worthy of notice. In the mole the first ster nal bone is very large and compressed. To its anterior pointed extremity the thick short clavicles are attached, and further back to the same bone, the first rib is articulated ; to the second bone is fixed the second rib, and there succeed to these three elongated bones of the ordinary form, to each of which two pairs of ribs are articulated ; then a small hone, to which one pair of ribs is fixed, and then the xiphoid bone, which is long and narrow.
In the Chrysochloris the first brine of the sternum is equally compressed but less elevated ; and the anterior half is furnished on the up per part with two small aliform processes, which are concave, and support the first two ribs, which are extremely broad ; the long slender clavicles are attached at its anterior point; and then follow seven other oblong pieces, and an elongated xiphoid bone, which bears at its posterior extremity a semilunar car tilaginous dilatation.
The ribs in the mole and its congeners are nearly all of the same length, giving that pe culiar cylindrical form to the body which cha racterises these animals, and which is so essen tial to their habits ; and in the Chrysochloris the first rib is very much broader than the others.
But it is in the bones constituting the anterior extremities, that the most remarkable and in teresting, peculiarities exist in some of the families of this group. In the mole especially, the anterior extremity (fig. 442) exhibits one of the most extraordinary modifications to be found in the whole of the Mammifera. The clavicle is fully developed in the whole of the Insec tivora. In the mole (b) it offers the most abnormal deviation from the usual construc tion. 1 t is extremely short and broad, forming in fact nearly a square ; about the middle of its anterior margin a strong process rises, which gives origin to the subclavian muscle, which in this animal is greatly developed. It is articu lated, as usual, with the sternum by its interior extremity, which may here be more properly called its interior margin ; but by its external margin it is connected moveably with the head of the humerus, which connection is rendered more solid towards the anterior part by a strong ligament. Its connexion with the acromion of the scapula is by a ligament merely, which extends from the acromion to the posterior and outer angle of the clavicles. In Condytura and
even in Scalops the construction of this bone is on a similar type; but in Chrysochloris it is long and slender as in the other Insectivont.
The scapula (a) in the mole is no less singu larly formed than the bone just described. It is elongated to au extraordinary degree, being not less than six times as long as it is broad at the broadest part,which is at the superior extremity. Towards the middle it is contracted and almost cylindrical ; and the spine, which runs nearly the whole length of the bone, is at this part almost effaced. The acromion, as before ob served, has only a ligamentous connexion with the clavicle. In Cundytura and Scalops the construction of this bone is somewhat similar, and in Chrysochluris it is also of considerable length.
The humerus in the mole (figs. 442, c, 443) is of so extraordinary a form, that were it examined alone, isolated from its natural con nexions, it would be impossible to detect its true character. It is of a square form, extremely broad at the superior part, where it presents two articular surfaces ; the an terior is very broad, slightly convex ; the posterior and internal is narrow, but more convex than the former ; by the first it is articulated to the clavicle, and by the latter to the scapula. Between the former, which may be considered as appertaining to the greater tuberosity of the bone, and the head, is a deep fossa. The body of the bone is short, thick, and very broad, and is curved upwards, sn that its articulation with the forearm is placed actually higher than the shoulder, and the palm of the hand is consequently turned outwards. In Chrysochloris the form of this bone is not less remarkable. It is somewhat longer than that of the mole ; its articulation with the forearm constitutes half a sphere ; and the inner condyle is so elongated and inclined downwards, that the whole bone forms an arch of which the convexity is turned outwards. This condyle is articulated with a bone, 'which must be considered as a most extraordinary modification of the us pisifurme, which is as long as the radius, so that in fact the forearm may he said to be composed of three bones.