MYOLOGY 31 



M. stylohyoideus (figs. 7, 8, 23, 24) has origin from 

 the base of the paroccipital process deep to the origin of 

 the digastric. Insertion is upon the greater cornu of the 

 hyoid. In Homodontomys this muscle is hardly larger 

 than the posterior termination of the hyoglossus, while in 

 Teonoma it is at least twice the mass, extending more 

 antero-laterad and being more strongly inserted upon 

 both the cranial and caudal borders of the cornu. In 

 Neotoma it is intermediate in development. 



Innervation is apparently by the N. facialis. 



M. transversus mandibularis (figs. 7, 24) is an un- 

 paired muscle connecting the two mandibular borders 

 just caudad to the symphysis menti. It has attachment 

 upon either side in rather illy-defined fossae. 



M. mylohyoideus (figs. 7, 24) has origin from the medial 

 surface of the ramus of the mandible, extending from 

 near the root of the first molar to a point just caudad of 

 the root of the last molar. Insertion is with its fellow 

 into the medial raphe, and onto the cranial border of the 

 hyoid bone. 



This muscle and the transversus mandibularis are both 

 served by the inferior alveolar nerve. 



IV. Muscles of the tongue 

 This group, as here defined, is composed of 



Mm. styloglossus genioglossus 



hyoglossus 



M. styloglossus (figs. 8, 23, 24). The origin of this 

 slender muscle should apparently be considered as from 

 the slight process upon the infero-posterior margin of the 

 auditory meatus rather than from the mastoid, as is usually 

 stated to be the case in rodents. Extending forward im- 

 mediately entad to the ramus of the mandible, insertion 

 is into the tongue through the cranio-lateral portion of its 

 base. 



