1896.] MYOLOGY or nODENTS. 183 



Adductor Indicis.— The adductor indicis was present in all -the 

 animals examined except Buthyergus, Georychus, a,nd Heteromys; 

 in the latter it was replaced by an adductor liallucis, which in the 

 other specimens was wanting, although Windle describes it in 

 Hydromys '. 



Prof. Cunningham has pointed out (Journ. of Anat. vol. xiii. 

 p. 11) that the foot of Bathyergus is peculiar in the total absence 

 of plantar adducting and dorsal abducting muscles. This state- 

 ment, which also applies to Georychiis, I am able to corroborate. 

 The muscle which I have described as abductor hallucis corresponds 

 to Prof. Cunningham's inner head of the flexor brevis hallucis, 

 though in his specimen the origin of the muscle was not so far 

 back as in mine. In no Eodeut were any distinct dorsal inter- 

 osseous muscles found. 



Interossei. — There are two interossei, or flexores breves, to each 

 toe inserted into the sesamoid bones beneath the metacarpo- 

 phalangeal articulation. 



Myohgical Oharacterisiics of tlie various Families of MyomorpJia. 



The animals of which the muscles have been described furnish 

 examples of four families of the JVlyomorpha, namely the Myoaddce, 

 Muridce, Spalacidce, and Geomyidce, Unfortunately the first and 

 last of these are each represented in my dissections by only one indi- 

 vidual, and for this reason any generalizations must be made very 

 tentatively. Still it seems worth while making an admittedly 

 imperfect contribution in the hope that it may be added to and 

 corrected whenever fresh material is available. 



In the first place, taking Myoxus dryas as a type of the Myoxida, 

 one notices that : — 



1. The biceps cubiti is only inserted into the radius. 



2. The coraco-brachialis is only represented by the second part. 



3. The palmaris longus is absent. 



4. The flexor sublimis digitorum is inserted into the fifth digit 

 as well as into the second, third, and fourth. 



5. The extensor minimi digiti is only inserted into the fifth digit. 



6. The trapezius has the second and third parts fused. 



7. The trachelo-mastoid is absent. 



8. The rectus abdominis does not decussate at its origin with its 

 fellow of the opposite side. 



9. The gracilis is single. 



10. The soleus rises from the middle of the fibula instead of 

 from the head of that bone. 



11. The tendon of tlie tibialis posticus lies in the same groove 

 as the flexor fibularis instead of in one of its own. 



In the Geomyidce, of which Heteromys longicitudatus is the only 

 representative dissected, the following points are of interest : — ; 



1. The digastric approaches the hystricoiDorphine type. 



2, The semitendinosus has only the caudal head present., 



' P. Z. S. 1887, p. 58. 



