270 ZAGLOSSUS. 
largely hidden by the mylohyoideus, a thin muscular sheet from the posterior 
portion of the ramus, beginning some 15 mm. behind the symphysis. The 
two sheets of opposite sides unite medially by a raphe and insert at the anterior 
end of the larynx. The myloglossus is exposed by laying back the mylohyoideus. 
It is attached on the ventral side of the skull from near the base of the ear on 
its medial side, forward to the angle of the jaw. It joins the opposite muscle 
at the midline. 
MUSCLES OF THE FORE LEG.— What appears to represent the deltoideus 
is present in both the Echidna and the Proechidna as a narrow band arising 
for a length of about 15 mm. along the anterior edge of the scapula, and at 
about the same distance dorsal to the junction of the acromion with the cora- 
coid. It narrows to a round stout tendon, that passes anteriorly to the fore 
leg to its insertion on the anterior side of the tuberosity of the humerus under- 
neath the insertion of the pectoral muscles. This muscle is what Mivart con- 
siders a second portion of the deltoid, whose main division he regards as the 
muscle from the clavicle to the pectoral ridge of the humerus. As already 
noted, the homology of this larger muscle is somewhat doubtful. From the 
fact, however, that in the Proechidna, its origin is wholly from the clavicle 
and its insertion is continuous with those of the other muscles of the pectoralis 
group, it seems better to consider it a clavopectoralis. 
Owing to the fact that in monotremes the anterior edge of the scapula 
corresponds to the scapula spine of other mammals, the relations of the muscles 
in this region differ accordingly. 
The supraspinatus arises from the entire medial surface of the scapula 
below the insertion of the serratus. It passes out beneath the acromion and 
episternum and inserts on the anterolateral extremity of the greater tuberosity 
of the humerus. 
The infraspinatus takes origin from the ectal side of the scapula, from 
the anterodorsal angle to the acromion and nearly to the glenoid cavity. It 
inserts on the greater tuberosity of the humerus just posterior to the insertion 
of the supraspinatus and continuous with it. The condition of these muscles 
in the Echidna is quite similar. 
The subscapularis occupies the entire posterior half of the ectal side of 
the scapula from the vertebral edge, posterior to the ridge above the glenoid 
cavity. It becomes tendinous and passes to the extremity of the lesser tuber- 
osity of the humerus. From the ridge between it and the infraspinatus comes 
the long head of the triceps. Westling has described in the Echidna a sub- 
