162 MR. F. G. PARSONS ON THE (Jan. 14, 
and runs down to be inserted, also by a narrow flat tendon, just 
external to the former and covering its insertion. This part is 
especially well marked in Heteromys. This arrangement, which is 
present in all the genera of the Muride that I have dissected, 
shows that, as the two muscles coexist in the same animal, they 
cannot be homologous, and I am now of opinion that the so-called 
Fig. 3. 
ANT. DEEP MAS, ‘ 
 Ays/ricomorphine, 
4 Soe = = 
ANT! Sup.Mas, +ANT. DEEP MAS. 
Sczwromorphine, 
Masseter of Heteromys. 
anterior deep part of the Scinromorphine masseter is an extension 
forward of the posterior superficial plane of fibres. The arrange- 
ment in the Spalacidee gives a clue to the way in which the infra- 
orbital slip appears ; in these animals it is very feebly marked, rises 
from the margins of the infraorbital foramen, and runs back to 
blend with the temporal instead of having an independent insertion 
opposite the anterior cheek-teeth. 
Facial Muscles——These muscles are best developed in the 
Spalacidee, especially in Bathyergus. In this animal the frontalis 
is continuous dorsally and laterally with the superficial panniculus, 
and the muscles of the small auricle are extensions from this. 
The orbicularis palpebrarum in Bathyergus is very small, corre- 
sponding to the feeble development of the eye. The levator labii 
superioris corresponds with the description of it in the other 
Rodents’. The dilatator naris rises deep to this and passes to the 
1 PZ. 8. 1894, p. 253. 
