MUSCULATURE. 275 
the other heads and completely covered by them, which arises from the ectal 
border of the internal epicondylus under head 2 and passes into a tendon which 
unites with the main tendon at the wrist. The large common tendon covers 
the palm and at the base of the metacarpals divides into three strong flat ten- 
dons, one each to digits 2, 3, and 4. Each tendon runs along the inferior side 
of its digit, and just distal to the base of the metacarpal passes through a trans- 
verse loop. It inserts in the terminal phalanx of the digit. This muscle in 
the Echidna differs remarkably in that there are five divisions of the great ten- 
don, one each to the five claws. According to Mivart each tendon likewise 
passes through a cross-loop at the metacarpal, except that of the pollex, but 
Fewkes found that division as well passed through a loop. In the Proechidna, 
therefore, the division into three instead of five tendons is correlated with the 
reduction of the clawed digits to three, showing that this difference is of a some- 
what profound character, functional as well as anatomical, for there is no trace 
of the two lost branches to the now reduced first and fifth digits in the Pro- 
echidna. In all other respects, however, the muscles of the fore limb are essen- 
tially alike in the two animals. It would be interesting to know the condition 
of this muscle in the occasional specimens of the Proechidna with more than 
three claws. 
The luwmbricales are four in number arising from the great pad of the 
profundus tendon; the two muscles of the first pair pass distally to the fascia 
surrounding metacarpals 2 and 3 respectively, those of the second pair pass in 
like manner to the approximated sides of metacarpals 3 and 4. The two middle 
muscles of these four are practically fused into a single mass. 
From the dorsal (carpal) side of the pad of the profundus arise three other 
small and flattened muscles:— the first originates between the tendons to 
digits 2 and 3 and passes to the fascia between those digits; the second takes 
origin from between the tendons to digits 3 and 4 and in like manner passes 
to the fascia between them; the third muscle arises slightly external to the 
base of the tendon of digit 4, and goes to the fascia between digits 4 and 5. 
There are in addition seven other small muscles in the deeper portion 
of the hand. Three of these arise from the tendinous insertion of the flexor 
carpt radialis, the most external of which passes to the end of the first digit 
on the radial side. It is very probably the homologue of the adductor pollicis 
(Plate 1, fig. 3, ap) and is present likewise in Echidna. The two other small 
muscles pass one to the radial and one to the ulnar side of the second digit 
and insert on its first phalanx. In a similar fashion, two other small muscles 
