REPORT ON THE MARSUPIALIA. 117 



This inner head is very graphically represented in the drawings of the foot 

 of the Cynoeephalus maimon which accompany BischofFs memoir upon the Hylobates 

 leuciscns (PI. IV. fig. 1, h, and fig. 2. III.). It can also be seen, although less 

 distinctly, in Euge's figures of the feet of the Cebus apella and Orang (pi. xxxv. figs. 52, 

 53 and 54). In the Cynoeeplialus sphinx it is very evident, and its association with the 

 outer head of the flexor brevis minimi cligiti is marked not only by its lying upon the 

 same plane, but also by both having a common origin from the base of the fifth meta- 

 tarsal. In the foot of the Ateles (?) it has a corresponding origin, but as we trace it towards 

 the metatarso-phalangeal joint it sinks gradually into the fourth inter-metatarsal space, 

 and is inserted into the extensor tendon on the dorsum of the first phalanx of the 

 minimus. In the Lemur it presents precisely the same disposition as in the preceding 

 animal. 1 



With regard to the other members of the intermediate group, a considerable reduction 

 takes place in the number of their elements. In Cynocephalus sphinx the flexor brevis 

 indicis is represented by the outer head alone, and the flexor brevis annularis by the inner 

 head alone. These muscles are distinguished from the dorsal interossei not only by their 

 insertions but also by being altogether invisible from the dorsal aspect of the foot. The 

 flexor brevis medii is represented by a single small fleshy slip, which arises from the base 

 of the fourth metatarsal bone and, crossing the third metatarsal obliquely, joins the second 

 dorsal interosseous muscle near its insertion. In BischofFs drawings of the foot of the 

 Cynocephalus maimon (before referred to) the inner head of the flexor brevis annularis, 

 and the outer head of the flexor brevis indicis are figured, but they are named the 

 second and first plantar interossei. The flexor brevis medii is evidently completely 

 gone. In the Ateles (?) a similar arrangement is observed, but here indications are to be 

 found which would seem to point to the fact that the lost elements of the intermediate 

 layer have coalesced with certain of the dorsal interossei. On removing the plantar 

 adducting muscles, and also the two heads of the flexor brevis minimi cligiti, we are 

 confronted with what appear to be three bicipital muscles lying upon the second, third, 

 and fourth metatarsal bones. These strongly resemble the amalgamated flexores breves 

 and dorsal interossei of the tetradactylous carnivora. A closer examination, however, and 

 an inspection of the dorsal aspect of the foot, will show that the muscles under consideration 

 consist of four bipenniform dorsal interossei, the outer head of the flexor brevis indicis and 

 the inner head of the flexor brevis annularis. The short flexors of the index and annularis 

 are placed not only upon the side, but also upon the plantar aspect of the corresponding 

 metatarsal, and they are united by their margins with the first and fourth dorsal 

 interossei respectively. Further, it is very evident that fibres which appear to rise with 

 those of the short flexors are prolonged upon the thick rounded tendons of the first and 



1 Thi; two heads of the flexor hrevis minimi digiti are well seen in fig. 30, pi. vi., illustrating Mnrie and Mivart's 

 Memoir upon the Lemuroidea. 



