632 



INSECTIVORA 



the young — generally from four to six in 



brought 



Fig. 290. — Skeleton of Mole x § (lower jaw 

 removed to show base of skull), c, Calcaneum ; 

 c.h., clavicular articulation of the humerus ; el., 

 clavicle; e.c, external condyle of humerus; /., 

 femur ; fb, fibula ; /c, falciform bone (radial sesa- 

 moid) ; h, humerus ; i.c, internal condyle of 

 humerus ; il, left ilium ; i.p, ramus of the ilium 

 and pubis; is., ischium; l.d, ridge of insertion of 

 latissimus dorsi muscle; l.t, lesser trochanter; m, 

 manubrium sterni ; o, fourth intercentral ossicle; 

 ol, olecranon ; p., pubis widely separated from that 

 • if the opposite side; j«t., patella; p.m., ridge for 

 insertion of pectoralis major muscle; pt., pectineal 

 eminence; r, radius; rb, lirst rib; x, plantar scsa- 

 noid ossicle corresponding to the radial .sesamoid 

 (os falciforme) in the maims; sc, scapula; s.h., 

 scapular articulation of the humerus; /. tibia; ». 

 ulna. 



number — which are 

 forth in about six 

 weeks, quickly attain then- 

 full size. 



The Mole exhibits in the 

 whole of its organisation a 

 joerfect adaptation to its 

 peculiar mode of life. In 

 the structure of the skeleton 

 (Fig. 290) very striking de- 

 partures from the typical 

 mammalian form are notice- 

 able. Thus the presternum 

 is so much produced anteriorly 

 as to extend forward as far as 

 a vertical line from the second 

 cervical vertebra, carrying 

 with it the very short and 

 almost quadrate clavicle, which 

 is articulated with its anterior 

 extremity and distally -with 

 the humerus ; being also con- 

 nected ligamentously with the 

 scapula. The fore limbs are 

 thus brought opposite the 

 sides of the neck, and from 

 this position a threefold ad- 

 vantage is derived : in the 

 first place, as this is the 

 narrowest part of the body, 

 they add but little to the 

 general width, which, if in- 

 creased, would lessen the 

 power of movement in a 

 confined space ; secondly, this 

 position allows of a longer 

 fore limb than would other- 

 wise be possible, and so in- 

 creases its power; and, thirdly, 

 although the entire limb is 

 relatively very short, its an- 

 terior position enables the 

 animal, when burrowing, to 

 thrust the claws so far for- 

 ward as to be in a line with the 

 end of the muzzle, the import- 





