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 loo^). 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 lumbricales 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 metacaipals 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 smgle mass. 



From the dorsal (carpal) side of the pad of the profundus arise three other 

 small and flattened muscles: — the first origmates 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 

 carpi 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 



