30 FIELD MUSEUM or NATURAL HISTORY ZOOLOGY, VOL. XIV. 



upper side of the one succeeding. Anteriorly it is closely associated 

 with the psoas parvus. 



Psoas parvus. Arises fleshy and also by tendinous heads from the 

 first, second, third, fourth and fifth lumbar vertebrae. Thence it 

 continues caudad as a broad flat tendon crossing the surface of the medial 

 part of the psoas magnus and inserting dorso-craniad of the marsupial 

 bone on the iliopectineal tubercle. In its cranial part it is closely con- 

 nected with the quadratus lumborum which lies laterad of it. The caudal 

 part of its fleshy origin on the fifth lumbar vertebra is overlapped by the 

 psoas magnus which intervenes between it and the quadratus lumborum 

 at this point. 



Psoas magnus. Origin from the sides of the bodies and the ventral 

 bases of the transverse processes of the fourth, fifth, and sixth lumbar 

 vertebrae and the cranial half of the first sacral. Anteriorly it reaches 

 to the posterior epiphysis of the third lumbar. Insertion with the 

 iliacus on the lesser trochanter and the adjacent inner surface of the 

 femur nearly as far distad as the insertion of the pectineus. 



i 



MUSCLES OF THE HEAD. 

 Plates III-IV. 



Masseter. The superficial masseter has its origin on the lower side 

 of the zygoma by a short stout tendon nearly opposite and slightly 

 caudad to that of the inferior zygomaticus and in the vertical plane of 

 the middle of the eye. It spreads over the lower part of the mandibular 

 insertion of the deep masseter and covers the ventro-caudal part of 

 the mandible with its insertion from the base of the coronoid process 

 just caudad of the buccinator and along the lower side of the mandible 

 to the angle and the pterygoideus. It does not reach the inner surface of 

 the mandible and especially in its ventro-caudal portion is relatively 

 weaker than in Didelphis. The deep masseter lies below it and is closely 

 connected, but a division is evident. It has its origin on the inner and 

 lower sides of the zygoma and the fascia over it and is intimately asso- 

 ciated with the temporalis. It is broadly attached to the whole outer 

 face of the coronoid fossa. 



Temporalis. This is in two layers. The superficial or outer temporal 

 arises from the fascia along the middle of the parietal bone and across 

 the caudal part of the underlying layer. Thence it spreads as a rather 

 thin sheet over the deep temporal and narrows to pass into the orbital 

 fossa and insert on the mandible at the anterior base of the ascending 

 ramus. It is also attached superficially to the membrane between it and 

 the eye. The deep temporal is more extensive; its origin runs from the 



