MUSCULATURE. 281 



probably represents the flexor longus hallucis, and possibly gives rise to some of 

 the small tendons described in connection with the longus digitorum as going 

 to the bases of digits 2 and 3. 



In the Echidna, the condition described for the flexors is quite different. 

 There are five tendons described by iVIivart, from the flexor longus digitorum, 

 one to each of the five phalanges, and no flexor longus hallucis. Westling and 

 Cunningham, however, found but four tendons from the longus digitorum, 

 one each to digits 1 to 4. The small longus hallucis was not found in the Echidna 

 by Mivart or Westling, nor does either mention the two additional small tendons 

 from the plantar pad to digits 2 and 3, that are present in the Proechidna, appar- 

 ently as parts of the flexor longus hallucis. 



Three small muscles representing the lumbricales arise from the inferior 

 side of the plantar pad and pass to the bases of the second to fourth digits re- 

 spectively as small tendons. On the dorsal side of the plantar pad three other 

 small muscles arise and pass to the third, fourth, and fifth digits respectively, 

 on their external sides. 



The tibialis posterior is a large muscle, nearly the size of the flexor longus 

 digitorum. It arises from the proximal three fifths of the lateral and posterior 

 sides of the fibula and from aponeurosis between tibia and fibula. It is covered 

 in part by the heads of the soleus, plantaris, and flexor longus, and passes to a 

 stout tendon running in the groove between the tibia and fibula just medial to 

 the spur, and inserts into the proxunal end of the astragalus. The condition 

 in the Echidna is quite the same. 



The peroneus longus (Plate 1, fig. 1, pi) is the most lateral of the lower leg 

 muscles. It originates on the external side of the head of the fibula for about 

 15 mm. beginning just below the tip of tlie proximal extension. It tapers to a 

 stout flat tendon as it reaches the end of the shaft, passes over the epiphysis 

 of the fibula, and thence through the groove on the peroneal tubercle of the 

 calcaneum, after which it goes to the ventral side of the foot to its insertion 

 on the proxmial edge of the fifth metatarsal; a small branch from the inserting 

 tendon crosses the foot to the basal phalanx of the first digit. In the Echidna 

 the condition seems to be much the same, although neither Mivart not Westling 

 mentions the msertion of the tendon into the fifth metatarsal, which is a promi- 

 nent feature in the Proechidna. 



The remaining extensores of the hind foot are essentially the same as in 

 the Echidna although apparently differing in a few slight details. The homology 

 of these muscles is not altogether certain. 



