MAMMALIA. 539 
cartilage, it probably represents the clavicle and precoracoid 
joined in one. Its distal end forms an attachment for the 
humerus and it is also joined by a ligament to the scapula. 
The scapula is long and narrow and assists, as usual, in 
bearing the humerus. The bony connection of “clavicle,” 
episternum, ribs and vertebral column, assisted by the 
scapula, forms a solid fulcrum for the fore-limb. The 
humerus is quite unique. Short and stout, it is expanded 
into lateral crests and processes. The radius and ulna are 
also short and stout and the olecranon is long, increasing 
the mechanical advantage of the extensor muscles. 
Fig. 372,ANTERIOR VIEW OF PECTORAL GIRDLE AND LIMB 
or THE MOLE. ; 
Note the shortened limb, powerful clavicle and humerus and 
broad scoop-like manus. 
The carpal bones are compact and the whole manus is 
broad and flat. There are five short digits with strong 
claws. Inside the first digit is a falciform bone which 
some authorities regard as a prepollex or sixth digit. What- 
ever its homology, it assists greatly in adding to the 
“expanse” of the hand. The movement of digging, like 
those of swimming and flying, involves a great development 
of the pectoral muscles; and in correlation with this there 
is a median keel or ridge on the sternum at their point of 
origin (¢f bat and bird). All the above structural features 
point to the burrowing function of the fore-limbs. With 
regard to the forward extension of the episternum, and with it 
