MAY, 1921. AMERICAN MARSUPIAL, C^ENOLESTES OSGOOD. 31 



glenoid fossa across the mastoid bulla along the supraoccipital crest 

 halfway to the median line and thence directly forward along the 

 rather indistinct parietal and supraorbital crests to the plane of the 

 posterior canthus of the eye. Its insertions are extensive on the coronoid 

 process, mostly on its ental surface and its anterior edge with a few of 

 the fibers from the mastoid origin going to its ectal surface. 



Buccinator. Relatively extensive and forming a pouch behind the 

 angle of the mouth. Its origin is along the alveolar border of the maxil- 

 lary from the vicinity of the infraorbital foramen to the anterior base of 

 the zygoma and likewise along the ramus of the mandible from the front 

 and base of the coronoid process forward to the vicinity of the mental 

 foramen. It is attached to or merged with the orbicularis oris around the 

 lips. 



Pterygoideus internus. Origin from the whole of the external 

 pterygoid fossa from the carotid foramen cephalad, passing the tips of 

 the pterygoids but attached to their bases and thence along the ridge to 

 the dorsal side of the lateral tuberosity of the palatal ridge. Insertion 

 broad on the inner surface of the angle of the mandible and by certain 

 medial fibers running to the fascia over the tympanic. Mediad of the 

 internal pterygoid the small but distinct tensor iieli palatini runs from the 

 periotic and the edge of the basisphenoid to the hamular process of the 

 pterygoid bone. 



Pterygoideus externus. Origin by two heads. The larger ventral one 

 arises fleshy from the whole of the lateral base of the pterygoid bone 

 laterad of the pterygoideus internus. The smaller dorsal head arises 

 from the alisphenoid caudad and laterad of the sphenoidal fissure. The 

 two heads spread over the convex surface of the alisphenoid between 

 the sphenoidal fissure and the glenoid fossa and, after uniting as they 

 pass the front of the tympanic, insert at the base of the mandibular 

 condyle principally on the stylomandibular ligament. 



The muscle is relatively large and broad, bulking fully two-fifths as 

 much as the internal pterygoid. It is thus quite different from that of 

 Didelphis in which it is single-headed and very weak. It is described 

 (Macalister) in Phascolarctos as a "small rudiment crossing and insepa- 

 rable from the internal" and in Sarcophilus as "exceedingly feeble"; in 

 Myrmecobius also, it is weak and single (Leche) ; in Choeropus (Parsons, 

 1903, p. 67), it is unusual and inserts on the inside of the mandibular 

 ramus; in Petrogale (Parsons, 1896) and other kangaroos, it is small; 

 for most other marsupials, data are lacking. 



Mandibulo-auricularis. The only prominent ear muscle seems to 

 correspond to the one for which this name has been used by various 

 authors. It is a small subcylindrical muscle arising in the fascia between 



