REPORT ON THE MARSUPIALIA. 107 



The adductor indicis (p 2 ) is the smaller of the two, and is very apt to be overlooked. 

 They both arise by a common origin in the middle line of the foot from the ligamentous 

 structures on the plantar aspect of the tarsus, and superficial to the other intrinsic 

 muscles. Diverging from each other, they end in thread-like tendons which are inserted 

 respectively upon the inner side of the base of the first phalanx of the minimus, and upon 

 the outer aspect of the base of the same phalanx of the index. In both cases the insertion 

 is into the extensor tendon and dorsal to that of the corresponding flexor brevis. 



Intermediate layer (f 2 to f"). — The members of this layer are strongly marked. 

 On each metatarsal bone there is a powerful fleshy mass which, as it approaches the root 

 of the corresponding toe, divides into two heads. These embrace the root of the digit, 

 and are inserted partly into the sesamoids, and partly into the extensor tendon. 



Dorsal layer. — Not a trace of abducting muscles is to be discovered. They are 

 entirely lost. At the same time I am inclined to believe that they have coalesced with 

 the flexores breves. It is true that there is very little outward evidence of this, only in 

 fact, the presence of tendinous intersections traversing certain of the bellies of the flexores 

 breves in lines along which such a fusion would take place. 



Nerve arrangements. — The deep division of the external plantar nerve passes inwards 

 under cover of the adductors, and supplies all the intrinsic muscles. 



Bathyergus capensis (PL VIII. fig. 1) and Mm capensis. (Cape Mole and Cape Mouse). 



The feet of these two animals are pentadactylous, and the intrinsic muscles are 

 arranged upon identically the same plan in both. There is a total absence of the plantar 

 adducting and the dorsal abducting muscles. The intermediate flexores breves, however 

 are well developed, each consisting of two strong slips. 



Whether the plantar and dorsal muscles are absent from suppression or fusion with 

 the flexores breves it is impossible to make out. If it be due to the latter cause there are 

 certainly no traces of the fusion to be discovered. 



In both animals the same peculiarity in the arrangement of the intrinsic muscles of 

 the hand is to be observed. 



Castor fiber (Beaver). 



The specimen of this species which I had an opportunity of examining was in a very 

 putrid condition, but by a careful dissection of both feet I obtained a satisfactory view 

 of the intrinsic muscles and their nerves of supply. There is a marked deficiency in the 

 number of elements composing each of the three typical layers of pedal muscles, but those 

 which are lost are for the most part represented in the foot by fibrous bands. The nerves 

 have a very remarkable disposition. 



Plantar layer. — The only muscular element of this layer is the adductor hallucis. It 

 consists of a very minute short fleshy belly succeeded by a long slender fibrous band or 



