172 MR. F. G. PARSONS ON THE [Jan. 14, 
found is that the outer division of his extensor carpi ulnaris is 
really the extensor minimi digiti, the tendon of which has lost its 
digital attachments and has become inserted into the base of the 
fourth metacarpal bone. 
Supinator Brevis.—The description of this muscle given in the 
other Rodents applies to the Myomorpha, with the exception that 
in the latter a sesamoid bone is usually found in the tendon. 
The only animals in which this bone was wanting were Bathyergus 
and Georychus. The relationship of the tendon of the supinator 
brevis to the external lateral ligament of the elbow is interesting, 
in some cases, as in that of Bathyergus, there is a well-marked 
external lateral ligament, situated behind the tendon, but in 
others, of which Cricetomys is an example, the tendon itself seems 
to form the lateral ligament, and has the orbicular hgament 
attached to it. 
Extensor Ossis Metacarpi Pollicis.—In all cases this muscle rises 
from both bones, and is inserted into the base of the metacarpal 
bone. In the Gerbille its tendon was double. In Cricetus and 
Cricetomys it had an extra insertion into the radial sesamoid bone 
or palmar cartilage. 
Extensor Primi Internodii Pollicis—In every animal examined 
this was absent. 
Extensor Secundi Internodii Pollicis—This muscle was only seen 
in Georychus, where it was well-marked, it accompanied the 
extensor indicis and separated on the back of the hand. This 
arrangement is practically the same as that already described in 
Castor. 
Extensor Indicis—As in other Rodents the extensor indicis 
rises from about the middle of the back of the ulna, and is inserted 
only into the dorsal side of the-index. In Myowus it rises from 
the top of the back of the ulna close to the olecranon. In the 
Vole I dissected the tendon had acquired a secondary attachment 
to the prominent ridge on the back of the radius at its lower end, 
while the part of the tendon between this and the index was 
wanting. 
Palmaris Brevis—When a palmar ossicle is present, which is 
not so often the case as in other Rodents, the muscle is attached 
to it. When there is no ossicle it is attached to the palmar fascia. 
In Microtus and Bathyergus no palmaris brevis was found. 
Flexor Brevis Digitorum Manus.—This muscle was found in 
Cricetomys, Cricetus, Georychus, and Bathyergus. In the first three 
it arose from the palmar ossicle, but in the last from the fascia 
just external to the pisiform bone. 
Muscles of the Thumb.—In almost all cases the abductor pollicis 
can be made out, and has its origin from the palmar ossicle. The 
flexor brevis was made out with difficulty in Myoxus, Georychus, 
and Bathyergus ; in the two latter the thumb is provided with a 
pair of sesamoid bones, as in all the other fingers. Bathyergus 
has a prominent cartilaginous spur on the outer and inner side of 
the hand; these probably represent the prepollex and postminimus. 
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OE oe ee ee 
