1896.] MYOLOGY OF RODENTS. 187 
The union of the tendons in the sole has been already alluded 
to as not being entirely confined to the Hystricomorpha. 
In the following points the Dipodide resemble the Myo- 
morpha :— 
. The sciuromorphine arrangement of the digastric. 
. The presence of a transverse mandibular muscle. 
. The absence of the scapulo-clavicularis. 
. The presence of the omo-hyoid. 
. The absence of the splenius colli. 
. The origin of the levator clavicule (acromio-trachelian) from 
the atlas. 
The first three of these are very important and constant 
points, the latter three are sometimes noted in the Hystrico- 
morpha. 
On the whole I think that the myological points in favour of 
myomorphine tendencies for the Dipodide are far stronger than 
those in favour of hystricomorphine. 
Sore Whe 
GENERAL SumMARY oF Musonkes oF RopENTs. 
In order to complete my paper I propose to give a series of 
lists of the different points in which the four suborders of Rodents 
differ from and resemble one another, though the following pages 
are only tentative, and liable to require rearrangement as further 
material is added. They may, however, prove useful in directing 
the attention of future observers to the muscles deserving of 
special notice from a classificatory point of view, and they may 
also be of service in showing the muscles that are constant in 
Rodents nearly related, whatever their mode of life may be, and 
that may turn out to be equally constant in nearly related groups 
belonging to other orders. 
In a former contribution’ the differences between the Hystrico- 
morpha and Sciuromorpha are summarized. 
Differences between the Myomorpha and Hystricomorpha, 
1. The part of the masseter which passes through the infra- 
orbital foramen is usually small in the Myomorpha, large in the 
Hystricomorpha. 
2. The Myomorpha have the sciuromorphine arrangement of the 
digastric. 
3. The transverse mandibular muscle is present in the Myo- 
morpha, absent in the Hystricomorpha. 
4, The omo-hyoid muscle is always present in the Myomorpha, 
and may be present or absent in the Hystricomorpha. 
5. The acromio-trachelian (levator clavicule) always rises from 
the arch of the atlas in the Myomorpha. In the Hystricomorpha 
it sometimes rises from the basioccipital. 
6. The scalenus anticus is usually absent in the Myomorpha, 
usually present in the Hystricomorpha. 
1 P.Z,S, 1894, p, 294, 
