REPORT ON THE MARSUPIALIA. 45 



springs from the outer tuberosity and the outer surface of the shaft of the tibia and from 

 the interosseous membrane. In the Cuscus it is inserted into the plantar aspect of the 

 internal cuneiform bone and the base of the first metatarsal bone ; in the Thyladne it is 

 inserted into the base of the metatarsal bone of the index. 



Extensor long us hallucis (PI. V. fig. 3, g'). — This is present only in Cuscus, and is a 

 well-developed muscle, which lies almost completely under cover of the extensor longus 

 digitorum. It arises from the anterior prominence of the head of the fibula, from the 

 inner border of the fibula in its upper half and from the interosseous membrane. It makes 

 its appearance by passing forwards between the tibialis anticus and the extensor longus 

 digitorum, and its tendon is inserted into the ungual phalanx of the hallux. In some 

 Marsupials, according to Professor Macalister, 1 this muscle is inserted by two tendons into 

 the hallux and index, viz., Wallaby, Oppossum, Phalanger. 



Extensor longus digitorum (PI. V. fig. 3, c). — In the Cuscus this muscle has a very 

 limited origin from the anterior prominence of the head of the fibula, from the outer 

 tuberosity of the tibia, and from a ligament which bridges across between these two bony 

 projections. In the Thyladne its orgin is much more extensive, viz., from the anterior 

 aspect of the head of the fibula, from the inner surface of the same bone in its upper two 

 thirds, and also from a corresponding portion of the interosseous membrane. 



In the Cuscus the muscle ends in three tendons. Of these one (the intermediate) 

 goes to the ring digit, the outermost to the little toe, whdst the innermost divides into 

 two for the index and medius. Each of the lateral tendons sends a slip to strengthen 

 that for the large ring digit. 



In the Thyladne four tendons are given off by the extensor communis digitorum, and 

 these are inserted in the following manner : — (1) The outermost is inserted into the 

 minimus, (2) the second (counting from the outer margin of the foot) divides and sends a 

 slip to the annularis and medius, (3) the third also divides for the medius and index, (4) 

 whilst the fourth goes to the index alone. 



Peroneal muscles — This group of muscles comprises in each case (1) the peroneus longus, 

 (2) the peroneus brevis, and (3) certain fleshy slips which represent portions of the 

 extensor brevis digitorum. 



Peroneus longus. — This is a very powerful muscle in the Cuscus (PI. V. fig. 3, a 1 and 

 a 2 ), in the Thyladne it is not so strongly developed. In both it springs by two heads 

 which are separated from each other by the anterior tibial nerve. In Cuscus the one 

 head of the peroneus longus, a broad flat band, is superficial to the other, and springs f'r< »m 

 the anterior and posterior prominences on the head of the fibula and from the external 

 lateral ligament of the knee-joint ; the deep head arises from the outer aspect of the shaft 

 of the fibula in its upper half. A strong tendon (PL V. fig. 3, a') issues from the muscle ; 

 this passes downwards behind the external maleolus to the outer margin of the foot, where 



Loc. cit., p. 3. 



