2o6 



VERTEBRATE SKELETON 



Chiroptera. — The skulls of bats differ in the two sub-orders, the facial part 

 being long in Macrochiroptera (fig. 217), short in Microchiroptera, the latter 

 having the sutures fused early. The insect-eating Microchiroptera have a 

 sagittal crest for the temporal muscles. Orbit and temporal fossa are usually 

 continuous, but some have a postorbital process of the frontal, and Macrochirop- 

 tera have a complete postorbital bar. The foramen magnum is nearly vertical; 

 the broad occipital covers the mastoid. The greater part of the cranial wall is 

 formed by the parietals. 



The anterior part of the cranium is most normal in Macrochiroptera where 

 the premaxillae meet in the median line, as they do in a few Microchiroptera, 



but most of the latter group have small premaxillae 

 (sometimes absent) separated by a cleft which may 

 reach the incisive foramen. In these genera the 

 bones are connected by ligaments so that they 

 are moveable, features connected with the 

 reduction of the incisors. The maxillae often 

 contain large sinuses, expanding the bone exter- 

 ^ nally and giving a strange appearance to the 

 skull and internally reducing the nasal cavities 

 and restricting the conchas. The lacrimal fora- 

 men is in the facial part of the bone. The zygoma 

 is largely maxillary and squamosal, the zygomatic 



Fig. 



216. — Skull .of 

 latimanus. 



Scapanus 



Fig. 217. — Cranium of Pleropus edwardsii. 



bone being reduced or absent. Orbito- and alisphenoids are only partly ossified 

 and there is no separate optic foramen. The slightly ossified petrosal is loosely 

 connected with the cranium. It is not certain how far the bulla is tj^mpanic or 

 entotympanic. The ramus of the lower jaw is low, the coronoid process strong. 

 Dermoptera. — Galcopithccus, the only genus, has a vaulted skull, broad 

 and depressed in front, with a vertical occiput, large orbits, partly separated from 

 the temporal fossae by postorbital processes of both f rentals and zygomatics, 

 the latter bone contributing to the zygomatic arch and extending to the mandibu- 

 lar fossa which is limited behind by a postglenoid process. The lacrimal fora- 

 men is within the orbit. A foramen ovale is present, but no f. rotundum. 

 The tympanic bone forms both auditory bulla and external meatus, and the 

 alisphenoid shares in the wall of the tympanic cavity. The condyle of the lower 

 jaw is a transverse roller. 



