174 THE SKULL, [CHAP. 



cerebral cavity, large orbits, nearly vertical occipital plane, 

 large olfactory fossce, a well-developed zygomatic arch 

 sending up a postorbital process to meet a corresponding 

 one from the frontal so as either partially or completely to 

 encircle the orbit behind, and tympanics ankylosed with 

 the other cranial bones, dilated into a bulla, and pro- 

 duced externally into a tubular auditory meatus. The 

 face is generally elongated, and narrow anteriorly, but in 

 Galeopithecus it is broad and depressed. 



In the MacroscelidcZ) or Elephant Shrews, the auditory 

 meatus is very large, the tympanic bul la much inflated, and 

 there are sometimes also very large mastoid bullse. 



In Tupaia, the malar has a large, oval, longitudinal per- 

 foration. There are also in this genus, as in some of the 

 other Insectivora, vacuities in the palate, arising from defects 

 of ossification, like those found in many Marsupials. 



In the remaining Insectivora the cranial cavity is of small 

 relative size. The orbit and temporal fossa are completely 

 continuous, and there is often not even a trace of a post- 

 orbital process to the frontal or malar. 



In the Erinaceidce (Hedgehogs) and the Ccntetidcz the 

 tympanic is a mere ring unankylosed to the surrounding 

 bones, but a kind of bulla is formed by a lamella pro- 

 jecting from the basisphenoid to join its inner and inferior 

 edge. 



In Erinaceus and Gymnura the zygomatic arch is com- 

 plete, but slender, and formed chiefly by the processes of the 

 maxilla and squamosal, which meet each other, the malar 

 being a small splint-like bone attached to the outer and 

 under side of the middle of the arch. In the Centetida the 

 malar is entirely absent, and, as the zygomatic processes of 

 both maxilla and squamosal are very short, there is no bony 

 arch. Centetes (the Tenrec) has a remarkably elongated 



