110 THE VOYAGE OF H.M.S. CHALLENGER. 



The abductor hallueis is exceedingly small and closely applied to the tibial head of 

 the flexor brevis hallueis. In great part fibrous, it arises from the scaphoid, and is 

 inserted upon the inner side of the nodular first phalanx of the hallux. 



The second and fourth dorsal interossei are strong, single-headed muscles which act 

 as abductors of the index and annularis from the middle toe. There is no trace to be 

 found of the other two interosseous muscles. 



The abductor ossis metatarsi minimi digiti hardly deserves the name of a muscle. It 

 is merely a stout fibrous band with an admixture of fleshy fibres which presents the 

 attachments of this muscle. 



Nervous arrangements. — The intrinsic muscles are supplied in the usual manner — 

 the abductor and flexor brevis hallueis by the internal plantar nerve ; the others by the 

 external plantar. It is to be noted that the deep division of the latter nerve crosses the 

 foot subjacent to the plantar muscles, and that it gives off the digital branch for the 

 adjacent sides of the annularis and minimus. This branch reaches its destination by 

 emerging from under cover of the adductor minimi digiti. 



A comparison of the feet of the foregoing members of the Eodent order shows what 

 seems to be a tendency to the disappearance of the plantar and dorsal muscles, but a 

 retention of the intermediate muscles. The following table renders this evident : — 



& 



Plantar layer. 



Paca ..... Three etrongly developed adductors. 



Hare, ..... Two feeble adductors. 



Beaver, ..... One very weak adductor (with traces of a second). 



Bathyergus, ) None _ 



Cape Mouse, J 



Dorsal layer. 



Paca, ..... Four members of this group (two very weak). 



Beaver, ..... Four members of this group (one very weak). 



Hare, \ 



Bathyergus, > . . . . Nona 



Cape Mouse, ) 



Intermediate layer. 



Cape Mouse, \ 



Bathyergus, V . . . . Five members of this group. 



Paca, ) 



Hare, ..... Four members of this group. 



T> ( Three members of this group (with traces of two 



\ others). 



Further, according to St. George Mivart and Murie, 1 we may class with the Bathy- 



1 On the Anatomy of the Crested Agonti (Proc. Zool. Soc. Lond., 1866, p. 415). 



