54 FIELD MUSEUM or NATURAL HISTORY ZOOLOGY, VOL. XIV. 



osity of the fibula. A few fibers also arise from the outer base of the 

 peroneus brews. The outer head arises from the outer tuberosity of the 

 fibula and the inner surface of the fibular sesamoid. Its tendon lies deep 

 to that of the peroneus brevis and passes with it through the annular 

 ligament over the external malleolus. Distad it passes over theperoneal 

 tubercle of the calcaneum and down the side of the cuboid deeply im- 

 bedded in tissue. Turning to the under side of the tarsus, it passes over 

 the cuboid and after being somewhat enlarged and attached near the 

 base of the fifth metacarpal, it passes the bases of the third and fourth 

 metacarpals and goes to insertion on the inner base of the hallux. Its 

 course and insertion are thus much the same as in Phascolarctos , Pha- 

 langer and Didelphis. 



Tibialis posticus. A distinct muscle with its fleshy part lying be- 

 tween the flexor digitorum fibularis and the flexor digitorum tibialis. 

 Its origin is from the inner side of the outer tuberosity of the fibula, 

 from the expanded inner surface of the fibula and from septa of the 

 fibular flexor. Its tendon runs beneath that of the flexor digitorum tibialis 

 and crosses it midway to the ankle finally inserting on the palmar surface 

 of the scaphoid. 



Extensor brevis digitorum. This is in three distinct divisions two of 

 which are of fibular origin while the third is on the dorsum of the 

 foot. The first is a thin flat muscle arising from a small space on the 

 outer expanded surface of the fibula slightly mediad and distad of the 

 outer condyle. Its tendon runs through the outer malleolar ligament and 

 inserts in the fascia on the outer side of the base of the first phalanx of 

 the third digit. The second division is slightly larger in its muscular 

 part which arises subjacent to the first and between it and the extensor 

 hallucis longus. Its origin occupies the distal two-thirds of the proximal 

 half of the outer expanded surface of the fibula. The proximal part of the 

 fibula between the tuberosities is without muscular attachments and 

 directly in relation with the inner surface of the peroneus tertius which 

 overlies the above-described divisions of the short extensor. The 

 tendon of the second division passes the outer malleolus with that of the 

 first and proceeds over the dorsum of the pes to insertion in the fascia 

 on the outer side of the base of the first phalanx of the fourth digit. 

 These two divisions obviously belong to the peroneal group of muscles 

 and are quite as distinct as the others. They are united in Didelphis and 

 Dasyurus and send tendons to the second, third and fourth toes; in 

 Thylacinus and Myrmecobius, they are in three divisions (Leche). 



A very slender tendon imbedded in fascia crosses the third meta- 

 tarsal and connects the tendon of the second division with that of the 

 third or pedal division. The third division or extensor hallucis brevis 



