1896.] MYOLOGY OF RODENTS. 165 
paroccipital process, by fleshy fibres. The sterno-mastoid has the 
usual origin and is inserted by tendon into the base of the par- 
occipital process in front of the last muscle ; it is the larger muscle 
of the two. In Cricetomys the cleido-mastoid is not covered by 
the trapezius at its origin, it is, however, overlapped by the sterno- 
mastoid at its insertion. Inthe Gerbille the two muscles are con- 
tinuous at their origin, the cleido-mastoid being the larger and 
rising from the inner half of the clavicle. Riizomys resembles 
Cricetus, Myoxus, and the Murine in the origin of the cleido- 
mastoid being overlapped by the trapezius, and Cricetomys in the 
insertion being overlapped by the sterno-mastoid. In Hydromys* 
the cleido-mastoid is the smaller muscle and is overlapped at its 
insertion by the sterno-mastoid. In Georychus and Bathyerqus 
the cleido-mastoid is not overlapped by the trapezius ; in the latter 
the two muscles tend to fuse as in the Gerbille, but to a greater 
extent ; at their insertion they are completely fused and are attached 
by a narrow tendon to the base of the paroccipital process. 
Sterno-hyoid and thyroid.—In most cases these muscles have the 
human attachments. In Bathyergus, however, the sterno-hyoid 
misses the hyoid bone and continues on to the symphysis menti, 
in this respect somewhat resembling the arrangement found in 
Myopotamus*. In Hydromys the arrangement seems identicai 
with that of Myopotamus °. 
Omo-hyoid.—As in the Sciuromorpha the omo-hyoid is always 
present in the Myomorpha; it has the same attachments, never, as 
far as I have seen, being attached to the clavicle. ‘There is no 
central tendon. In Bathyergus the muscle is not attached to the 
hyoid bone, but is continued forwards with the sterno-hyoid to the 
symphysis menti. 
Levator Clavicule (Acromio-trachelian).—In all the animals 
examined this muscle rose from the anterior arch and transverse 
process of the atlas. Its usual insertion is into the acromial pro- 
cess, but sometimes it extends to the spine of the scapula. This 
description applies also to Hydromys*. In Bathyergus the muscle 
is very large and extends from the acromion on to the outer half 
of the clavicle at its insertion, in this respect resembling the 
Dipodide. 
Rectus Capitis Anticus Major and Minor and Longus Colli.— 
These muscles have the Hystricomorphine attachments. 
Scalene Muscles.—A scalenus anticus, that is a muscle passing 
to the first rib in front of the subclavian artery and brachial plexus, 
was only seen in the following animals—Gerbillus, Georychus, and 
Bathyergus. In these it resembled the same muscle among the 
Hystricomorpha, in rising from the basioccipital bone. The sca- 
lenus medius and posticus of human anatomy are represented by 
one mass, which rises from the transverse processes of all the cer- 
vical yertebre, passes behind the brachial plexus, and is inserted into 
1 P. ZS. 1887, p. 5 
2 P. ZS. 1894. p. 2 
2 PZ, 8. 1887, p. 5 
6. 
Ororor 
