EEPORT ON THE MARSUPIALIA. 67 



The adductor indicis (p 2 ) and adductor annularis (p 4 ) arise from the deep surface of 

 the greater part of the fibrous raphe under cover of the preceding muscles. They are 

 inserted one into the outer aspect of the base of the proximal phalanx of the index, and 

 the other into the inner side of the corresponding phalanx of the annularis. 



In this group of muscles we have another striking illustration of the tendency of the 

 marginal adductors to usurp the middle line by thrusting back the central adductors, 

 and coalescing in the middle line superficial to them. It is a further stage of what we 

 observed in Dasyurus, in which the adductors of the hallux, index, and minimus are upon 

 the same plane, and the adductor annularis upon a deeper plane. Here the adductors of 

 the hallux and minimus have come to lie superficial to the adductors of the index and 

 annularis. 



Ruge in his article upon the short muscles of the foot 1 figures and describes the 

 muscular and nervous anatomy of the pes of Didelyphys cancrivora. In this case the 

 adductor annularis as in Dasyurus is the only member of the adducting group which lies 

 under cover of the others. The adductor indicis is a weak muscle which springs from 

 the inner margin of a small portion of the lower end of the median raphe, and therefore 

 lies upon the same plane as the adductors of the hallux and minimus. 



Intermediate layer (f 1 toy 5 ). — Each digit is provided with a flexor brevis, and each 

 of these five muscles is composed of two slips. The two heads of the flexor brevis 

 hallucis are much more strongly developed than those of the other members of 

 this series. 



Meckel in the sixth volume of his work upon Comparative Anatomy (p. 466) states 

 that in Sarigues (i.e. Opossums) the short flexor of the hallux is absent. He adds 

 however, " the adductor is of medium size and divided into two heads which spring very 

 close to each other. . . . They go solely to the base of the first phalanx." Clearly he 

 looks upon the outer head of the flexor brevis as the caput obliquuni of the adductor 

 hallucis and the muscle which Dr. Young has named the adductor hallucis as being the 

 caput transversum, or in other words the transversalis pedis. Ruge in his description 

 of the foot of Didelphys cancrivora agrees with Meckel, and supports this view by assert- 

 ing that the muscle in question is supplied by the deep division of the external plantar 

 nerve. He says : — " The muscle for the first toe is already in Didelphys separated into 

 two heads. The part arising in common with the fifth contrahens {i.e., adductor minimi 

 digiti) represents the transverse head and the part from the base of the second meta- 

 tarsal represents the oblique head. Both heads are like the other contrahentes (i.e., 

 adductors) supplied by the external plantar nerve." The presence of the inner head of 

 the flexor brevis hallucis as a muscle distinct from the abductor hallucis is denied by 

 Ruge as well as by Meckel. 



1 hoc. cit., p. 54. 



