190 MR. F. G. PARSONS ON THE [Jan. 14, 
16. The gracilis is usually a double muscle in the Myomorpha, 
single in the Lagomorpha. 
The distinctions above given are possibly more numerous than 
they would be if the opportunity of dissecting a Pika (Lagomys) 
had presented itself. 
To merely point out the differences between the various sub- 
orders does not give a just idea of their muscular characteristics. 
It is necessary also to lay stress on the chief points in which one 
resembles another and differs from the rest. 
In the first place the Myomorpha resemble the Hystricomorpha 
and differ from both the other suborders in the following points :— 
1. A slip of the masseter passes through the infraorbital 
foramen. 
2, The three parts of the temporal are more closely fused. 
3. The rectus abdominis often decussates at its origin. 
4. The gracilis is usually double. 
5. The supracondylar slip of the semimembranosus often comes 
from the caudal vertebre. 
The Myomorpha resemble the Sciuromorpha and differ from the 
other two suborders in the following points :— 
1. The sciuromorphine type of the digastric. 
2. The presence of the transverse mandibular muscle. 
3. The constant presence of the omo-hyoid. 
4, The acromio-trachelian (levator clavicule) always rising from 
the atlas. 
5. The absence of the scalenus anticus in the Sciuromorpha and 
in the Myomorpha except the Bathyergine and Gerbillus. 
6. The absence of the scapulo-clavicularis in both, with the 
exception of the Bathyergine. 
7. The presence of the two heads to the biceps cubiti. 
&. The presence of the clayo-cucullaris part of the trapezius. 
9. The absence of the splenius colli. 
10. The presence of ischial and caudal heads to the biceps 
femoris, the latter being often more or less blended with the 
gluteus maximus. 
11. The fact that the flexor tibialis (flexor longus digitorum) 
does not join the flexor fibularis (flexor longus hallucis), except in 
Rhizomys, Leteromys, and partly in Pteromys. 
I have been unable to find any point of importance in which 
the Myomorpha resemble the Lagomorpha and differ from the 
other two suborders. 
The Hystricomorpha resemble the Lagomorpha and differ from 
the other two suborders in the following points :— 
1. The presence of the scapulo-clavicularis. 
2. The omo-hyoid is often absent in the Hystricomorpha, always 
in the Lagomorpha. 
ae, ee Te ni eee ee 
