188 MR, F. G. PARSONS ON THE [Jan. 14, 
7. The claviculo-scapularis is absent in the Myomorpha, present 
in the Hystricomorpha. 
8. In the Myomorpha the three parts of the deltoid lie close 
together. In the Hystricomorpha they are separated by distinct 
intervals. 
9. The biceps eubiti has two heads in the Myomorpha. In the 
Hystricomorpha there may be one or two. 
10. The Myomorpha seldom have the first part of the coraco- 
brachialis, in the Hystricomorpha it is often present. 
11. The splenius colli is never found in the Myomorpha, in the 
Hystricomorpha it is sometimes seen. 
12. The two parts of the biceps femoris are usually distinct 
in the Hystricomorpha. In the Myomorpha they are seldom 
separable. 
13. In the Myomorpha the flexor tibialis and flexor fibularis 
do not usually join in the sole. In the Hystricomorpha they are 
always united. 
14. In the Myomorpha the accessorius is absent or very ill- 
developed. In the Hystricomorpha it is present and _ well 
marked. 
Differences between the Myomorpha and the Sciuromorpha. 
1. The three parts of the temporal muscle are more closely 
fused in the Myomorpha than in the Sciuromorpha, 
2. A small part of the masseter passes through the infraorbital 
foramen in the Myomorpha. No part passes through in the 
Sciuromorpha. 
3. The three parts of the deltoid are more closely fused in the 
Myomorpha than in the Sciuromorpha. 
4, In the Myomorpha a rotator humeri is only found in the 
Cricetine. In the Sciuromorpha it is always present. 
5. In the Myomorpha the flexor sublimis digitorum sends no 
slip to the fifth digit. In the Sciuromorpha this slip is present. 
6. The supinator longus is absent in the Myomorpha, but is 
present in the Sciuromorpha except Castor’. 
7. The extensor longus digitorum always sends a tendon to the 
fifth digit in the Sciuromorpha; this tendon is often absent in the 
Myomorpha. 
8. The rectus abdominis often decussates at its origin with its 
fellow in the Myomorpha. There is no decussation in the Sciuro- 
morpha. 
9. The quadratus femoris is triangular in the Myomorpha, 
quadrilateral in the Sciuromorpha. 
10, The supracondylar ship of the semi-membranosus always 
rises from the tuber ischii and is closely connected to the 
adductors in the Sciuromorpha, In the Myomorpha it may rise 
from the tuber or caudal vertebre and is distinct from the 
adductor mass. 
1 Macalister describes an exceedingly feeble supinator longus in the Beaver 
(‘Morphology of Vertebrate Animals,’ p. 289). 
Se ee 
