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INSECTIVORA


form of what is known as the tritubercular sectoral type. There is no caecum.

The first representatives of this group are the moles, or Talpidae, in which the lower ends of the tibia and fibula are united (fig 3, Moles t, fb), there is a descent of the testes, the tympanum forms a bladder-like bulla, the zygomatic, or cheek-arch, although slender, is complete, there is no pelvic symphysis, the upper molars are five-cusped, and the first upper incisor is simple, and the lower vertical. In habits the majority of the family are burrowing, but a few are aquatic; and all feed on animal substances. The distribution is limited to the temperate regions of Europe, Asia and North America.

Throughout the family the eyes are minute, and in some species are covered with skin; the ears are short and hidden in the fur; and the fore-limbs are generally more or less modified for digging. The true moles of the genus Talpa are the typical representatives of the first subfamily, or Talpinae, in which the clavicle (fig. 3, cl.) and humerus (iz) are very short and broad, while there is an additional sickle-like bone (fc) on the inner side of the fore-foot. In Talpa itself the first upper incisor is but little larger than the second, the fore-foot is very broad, and the dental formula is i. 3, c.$, p. § . § , or § , m. There are about a dozen species, all confined to §

§

FIG. 2.~Pctcr's jumping-Shrew (Pelrodromus tetradactylus). the Old World. The variation in the dental formula of some of the best known of these

is as follows:-

i. § , c. 5, p. 1, m. § ><2 (T. wogura, robusta). 1. § , c. 1, p. 1, nz § ><2 (T. europaea, caeca, romana, hmgirostris, micrura).

52, c. {, p. § , m. § ~X2 (T. leucura leptura). 1. 3, c. }, p. ga, m. § ><2 (T. moschata). Except in T.

T micrura the

europaea, the eyes are covered by a membrane. In short tail is concealed by the fur. T. europaea extends from England to japan.

T. meta and T. romana are found south of the Alps, the remaining species are all Asiatic, two only—T. micrura. and T. leuturaoccurring south of the Himalaya.

The genus may be split up into subgenera corresponding with the above table; these subdivisions being sometimes accorded full generic rank. For instance the japanese T. 'wogum and the Siberian T. robusta are often referred to under the ill-sounding titles of M ogera wogura and M. robusta.

Referring more fully to the European species, it ma be mentioned that the mole exhibits in its organization perfect adirptation to its mode of life. In the structure of the skeleton striking departures from the typical mammalian forms are noticeable. The first sternal bone is so much produced as to extend forward as far as a vertical line from the second cervical vertebra, carrying with it the very short almost quadrate clavicles, which are articulated with its anterior extremity and externally with the humeri, being also connected ligamentously with the scapula. The fore-limbs are thus brought opposite the sides of the neck, and from this position a threefold advantage is derived:-in the first place, as this is the narrowest part of the body, they add little to the width, which, if increased, would lessen the power of movement in a confined space; secondly this position allows of a longer fore-limb than would otherwise be possible, and so increases its lever power; and, thirdly, although the entire limb is relatively short, its anterior position-enables the animal, when burrowing, to thrust the claws so far forward as to be in a line with the end of r

the muzzle, the import- ~i

ance of which is evident. 'lb

Posteriorly, we find the, Ifhind-limbs removed out of A 'I

the way by approximation ig, 'i' J of the hip-joints to the = ' ' ° é"'§ f9 centre line of the body.

This is effected by inward

YP Q; QUE

t 'MJF sy Ll]», v/17 [L

¢ fl r

curvature of the innomi-, itz; f*>" nate bones at the aceta- ' ('» ' Q bulum to such an extent V". ' f, '7-" that they almost meet in jQ7;'f-"A the centre, while the pubic a., *st- 07 lgolr1iesdare&v1idel¥ separated

e in e s ortness o, . "

the fore-limb is due to the 4

humerus, which, like the ' ,

clavicle, is so reduced in

length as to present the =?,53 &, appearance of a flattened ' " ”

X-shaped bone, with

prominent ridges and deep

15-@i§ ' i

n a | ';

depressions for the attach- 'Q

ments of powerful muscles. f;

Its upper extremity pre- » °

sents two rounded prominences;the smaller, thetrue "f N

head of the bone, articu- 1" ' i, '~, lates as usual with the /f, Q -

scapula; the larger, which ]¢, ~, fb A f .- / is the external tuberosity -', "Q'~ U g #QC rounded off, forms a se a- ) A i Ii? . rate joint with the endpof Y, I 5 rl #W the clavicle. This double fi ' 1, <articulation gives the !.

rigidity necessary to sup- I

port the great lateral 1

pressure sustained by the

fore-limb in excavating.

The bones of the fore-leg

are normal, but those of

the fore-foot are flattened

and laterally expanded.

The great width of the

fore-foot is also partly due

FIG. 3.-Skeleton of Mole (T alpa

europaea) (lower jaw removed to show base of skull).

to the presenceofapeculiar C, C31C3nCllmbgne on the inner Side Of C.h, Cl3.ViCUl3I' 3.I'tiCL1l8.lZlOIl of the the palm and articulating hurI}€rLlSwith the wrist. cl. Clavlcle-The

muscles acting on e.c, External condyle of humerus. these modified limbs are f. F§ %mL1rhomologous with those of fb, Flblllii-Cursorial insectivoragjiffer- fc, F alciform bone (radial sesamoid). ing only in their relative fi, HUm€1'l1Sdevelopment. The tendon 1.6, Internal condyle of humerus. of the biceps traverses a il, I-eff iliP1C b0H€long bony tunnel, formed Lp, Ramus of the ilium and pubis. by the expansion of the 'ny ISC|1iUmmargin of the bicipital Ld, Ridge of insertion of latissimus groove for the insertion dorsi muscle. of the pectoral is major l.t, Lesser trochanter. muscle; the anterior m, Manubrium sterni. division of the latter 0, Fourth hypapophysial sesamoid muscle is unconnected with ossicle. the sternum, extending ol, Olecranon. across as a band between p, Pubic bone widely separated the humeri, and co-ordi- from that of the opposite side. nating the motions of the pa, Patella. fore-limbs. Theteresmajor p.m, Ridge for insertion of pectoral is and latissimus dorsi major muscle. muscles are of immense pt, Pectineal eminence. size, inserted into the r, Radius. prominent ridge below the rb, First rib. pectoral attachment, and s, Plantar sesamoid ossicle correare the principal agents in sponding to the radial sesamoid the excavating action of (os falciform) in the manus. the limb. Time cervical sc, Scapula. muscles connecting the s.h, Scapular articulation of the slender scapulae, and humerus.

through them the fore- t, Tibia.

limbs, withthecentrelineof 14, Ulna. the neck and with the occiput

are large, and the ligament um nuchae between them is ossified. The latter condition appears to be due to the prolongation forwards of the sternum, preventing fiexion of the head downwards; and

accordingly, the normal office of the ligament being lost, it ossifies,