ANATOMY OF THE BEAVER. 59 



crest extends downward to the bottom of the bulla — 

 a long, rough process at the base connects it with the 

 basilar process and the post-sphenoid — it is separated 

 from the ala of the sphenoid by a large fissure — the 

 foramen lacenum basis cranii. The auditory canal is 

 prominent, extending upward, outward, and forward. 

 The styloid bone lies in a groove of the bulla, at- 

 tached by a ligament. The foramen for the Eustachian 

 tube is a little above the junction of the long process 

 of the sphenoid with this bone. The petrous portion 

 has an uneven surface within. Above the internal 

 auditory foramen is a pit which receives a process of 

 the cerebellum, in the margin of which is a semicir- 

 cular canal. The malar bones are long inferiorly. 

 The ascending portion in front is firmly united with 

 the transverse plate of the superior maxillary, the 

 edge of which is seen in front of the malar. Above, 

 the malar forms the outer third of the orbit — forming 

 a process from which a ligament extends to the frontal 

 to complete the orbital opening, separating the orbit 

 from the temporal fossa — this large fossa is bounded 

 laterally and posteriorly by the malar, temporal, and 

 parietal bones. 



The superior maxillary bone extends from the pos- 

 terior line of the molars to the interparietal, and forms 

 about half the arch between the incisors and the 

 molars — and less than half the sheath of the incisors. 

 The transverse malar plate commences at the back 

 part of the first molar, extends outwardly to the an- 

 terior inferior angle of the malar, forming, as seen 

 from in front, a broad arch. In front of the first 

 molar, a ridge commences, becoming more prominent, 

 and passing upward, parallel with the malar plate, 



