x.] CHIROPTERA. 177 



the horizontal plates of the palate bones being large and 

 early united in the middle line, without defects of ossifica- 

 tion. The pterygoids are small. There is no alisphenoid 

 canal. The glenoid fossa is broad and shallow ; the post- 

 glenoid process very little developed, and with a venous 

 foramen behind it. The tympanics are very slightly con- 

 nected with the neighbouring bones, and are consequently 

 nearly always lost in macerated skulls. A wedge-shaped 

 portion of the mastoid appears on the outside of the skull 

 between the squamosal and the exoccipital. The par- 

 occipital process is long and rather slender and directed 

 downwards and backwards. The periotic has a large and 

 deep fossa for the flocculus on its inner side. 



FIG. 58. Hyoid bones of Frugivorous Rat (Ptervfus) from below. M bosihyal ; 

 ty thyrohyal ; sh stylohyaL 



The mandible has a high, broad, recurved coronoid pro- 

 cess, a transversely extended condyle, and a flattened rounded 

 angle, without a distinct process. 



The hyoid (Fig. 58) has a narrow, transversely extended 

 basihyal, with which the elongated, laterally compressed and 

 curved thyrohyals are commonly ankylosed. The anterior 

 cornu contains three slender ossifications of nearly equal 

 length. 



The Insectivorous Bats generally have the skull shorter 

 and broader than the Pteropi. The cranial cavity in many 

 species is almost globular, with thin smooth walls, though 

 sometimes sagittal and occipital crests are developed. The 

 occipital foramen is very large. The zygoma is slender. 

 Postorbital processes are sometimes well developed, but 



