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 Mivart, from the fleror 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 to4. The smalllongus 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 lwmbricales 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 fleror 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 proximal end of the astragalus. The condition 
in the Echidna is quite the same. 
The peroneus longus (Plate 1, fig. 1, pl) 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 the 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 
caleaneum, after which it goes to the ventral side of the foot to its insertion 
on the proximal 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 insertion 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. 
