52 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



brane. Its large tendon passes inside the calcaneum where it becomes 

 broad and heavy and soon divides into four strong tendons bearing the 

 lumbricals and running to the ends of the outer toes. Just before the 

 common tendon divides it receives on its ental surface the two flattened 

 tendons of the flexor digitorum tibialis between which passes the flexor 

 accessorius. 



Flexor accessorius. Arises on the tuberosity of the distal outer 

 extremity of the os calcis, spreads over the ventral surface of the distal 

 part of the calcaneum, passes beneath the plantar ligament and then 

 becoming tendinous, continues diagonally entad of the common tendon 

 of the large flexor fibularis. Thence it perforates the tendon of the 

 flexor tibialis, or at least is somewhat attached to it, and proceeds to 

 insertion on the distal phalanx of the hallux. Just before passing 

 through the annular ligament at the first joint of the hallux its tendon 

 unites with that of the flexor tibialis. 



This muscle is present in Didelphis and has been described by Coues 

 (1872, p. 134) under the name flexor brevis pollicis obliquus. In Didelphis, 

 however, it passes ectad of the common tendon of the flexor fibularis 

 and its tendon joins the tendon of the flexor tibialis before it reaches the 

 hallux. An accessorius is recorded also for Chironectes (Sidebotham, 

 1885, p. 16). 



The accessorius is stated by Leche (Bronn's Thierr., p. 904) to be 

 generally lacking in marsupials and perhaps the above described muscle 

 should be regarded as a part of the flexor digitorum communis brevis 

 which is otherwise rather weak and slightly represented (seepostea, p. 57). 

 Whatever its name, it is evident that it is more independent in Ccenolestes 

 than in other marsupials or most other mammals, especially in the 

 distinctness of its tendon for a considerable distance on the hallux. 

 A somewhat similar accessorius found in an insectivore, Gymnura, is 

 regarded as abnormal by Parsons (1898, p. 324). It is of regular occur- 

 rence in edentates. 



Flexor digitorum tibialis. Origin from the greater part of the proxi- 

 mal half of the interosseous membrane, from the popliteus, and by a few 

 fibers from the inner side of the inner tuberosity of the fibula. Its tendon, 

 closely associated with that of the tibialis posticus, passes the inner mal- 

 leolus and soon divides into two, one of which runs directly to the ental 

 surface of the large tendon of the flexor fibularis and the other joins the 

 small tendon of the accessorius and after a lateral connection with the 

 main tendon of the fibular flexor it continues to an insertion on the 

 terminal phalanx 1 of the first digit. 



Peroneus brevis. Origin tendinous from the inner tuberosity of the 

 fibula and proximally by septa with the muscles lying on either side and 



