1896.] MYOLOGY OF RODENTS. 183 
Adductor Indicis.—The adductor indicis was present in all the 
animals examined except Bathyergus, Georychus, and Heteromys ; 
in the latter it was replaced by an adductor hallucis, 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 Georychus, 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 Rodent 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. 
Myological Characteristics of the various Families of Myomorpha, 
The animals of which the muscles have been described furnish 
examples of four families of the Myomorpha, namely the Myovide, 
Muride, Spalacide, and Geomyide, 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 Myoxide, 
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 the tibialis posticus lies in the same groove 
as the flexor fibularis instead of in one of its own. 
In the Geomyide, of which Heteromys longicaudatus is the only 
representative dissected, the following points are of interest :— 
1. The digastric approaches the hystricomorphine type. 
2. The semitendinosus has only the caudal head present. 
1 P. Z. 8. 1887, p. 58. 
