182 MR. F. G. PARSONS ON THE (Jan. 14, 
Plantaris.—This has the typical rodent arrangement, the only 
point of interest being the extent to which the muscular fibres of 
the flexor brevis digitorum are developed in the sole. In Gerbillus 
three little slips of muscle are alone seen in the intervals between 
the four tendens where they first separate. In Microtus the flexor 
brevis has no muscular fibres at all, while in Myowus and Myodes 
there are very few. All the other animals examined had well- 
developed muscular bellies to the flexor brevis. 
Popliteus.—The popliteus always rises from the external condyle, 
and is inserted into the upper part of the internal border of the 
tibia. 
Flexor Longus Hallucis (Flecor Fibularis).—This is always a 
large muscle, rising from both the tibia and fibula and being 
inserted into the distal phalanges of all the toes. 
Flexor Longus Digitorum (Flexor Tibialis).—Dobson? states that 
this muscle in the Myomorpha is always separate from the flexor 
fibularis tendon in the sole. I have, however, met with two 
remarkable exceptions to this generalization, viz. Rhizomys and 
Heteromys. In both of these animals the tendons unite in the sole 
exactly as they do in the Hystricomorpha. I should mention that 
this arrangement was present in both the right and left feet. In 
Georychus and Bathyergus the muscle is better developed than in 
most of the Myomorpha, and ends in a bone beneath the base of 
the first metatarsal which I am inclined to regard as a rudiment of 
a prehallux. In all the other animals examined the muscle ends 
chiefly in the fascia of the foot. 
Tibialis Posticus.—This is always a small muscle and rises from 
the upper part of the posterior surface of the tibia below the 
attachment of the popliteus, and also very often from the back of 
the head of the fibula. As a rule it has a groove of its own behind 
the internal malleolus, but in Myowus it shares the groove of the 
flexor fibularis. It is inserted into the under surface of the navi- 
cular, though in Mus rattus it goes chiefly to the plantar fascia. 
Muscles of the Foot. 
Lumbricales.—In Georychus, Bathyergus, Rhizomys, and Heteromys 
only three lumbricales are present. All the other animals dissected 
have four. 
Accessorius.—This muscle is very ill-developed in the Myo- 
morpha. The only animal in which I found it really well marked 
was in Bathyergus, although traces of it could be made out in Mus 
rattus. 
Abductor Hallucis—This is usually present and rises from the 
navicular in Cricetomys, Rhizomys, Mus barbarus, and M. rattus. 
In Gerbillus, Cricetus, Microtus, Myoxus, Heteromys, and Georychus 
it came from tle internal cuneiform. In Bathyergus it was well- 
marked and rose from the sustenaculum tali of the caleaneum, 
its proximal part forming the calcaneo-scaphoid ligament. 
Journ, Anat, xvii. p. 142, 
