INTEKRELATIONSHIPS OF GENERA 



37 



the braiucase and the attachment of their post-orbital tendons is 

 marked by the prominent peg-Hke post-orbital process of each 

 squamosal ; the anterior parts of these muscles produce an elevated 



Fig. 20. — Lcmmus lemtnus Linnaeus. 



Skull and left mandibular ramus dissected to show the alveolar courses 

 of the teeth (enlarged). 



superciliary ridge on each side, but they are not strong enough 

 as a rule to cause these ridges, even in old age, to fuse into an inter- 

 orbital crest and the squamosal bones remain widely separated 

 anteriorly. The cavity of the middle ear is partly filled with a 

 dense sponge of bone. 



