parietal 



orbitosphenoid 



orbitosphenoid 

 frontal 



maxilla' 



pterygoid de'ntary 



parietal 

 squamosal 



postporietal 



supraoccipital 

 capsule 



exoccipital 

 basioccipital 

 basisphenoid 



B 



palatine 



orbitosphenoid 



presphenoid center of orbitosphenoid 

 alisphenoid 



lingula of basisphenoid 

 foramen ovale and spinosum 

 tympanic 

 prearticular 

 malleus 



VII and VIII nerve roots 

 exoccipital 



D 



postparietal 



Figure 3-1. Head skeleton of early human foetus (3 months). A, lateral view; B, medial view of 

 right half of skull; C, half the skull as seen from below; D, half as seen from above with roof removed. 



specimen of a mammal. A biproduct of this e.\ercise is an 

 introduction to some of the problems of terminology. 



To establish terms more usable for comparative study than 

 those of the N.A., the names of several bones in the human 

 skull have been changed. These names are: os inaswutn, now 

 called prema.xilla and separated from the remaining bone 

 which retains the name maxilla; interparietal, now called 

 postparietal because it is more descriptive and frees inter- 



parietal for use for bones actually lying between the parie- 

 tals; zvgomaticus, now called jugal to agree with long-estab- 

 lished usage in comparative anatomy and to avoid the 

 descriptive inference of a zygomatic arch; minor cornua, now 

 called hypohyal to avoid a descriptive term not applicable 

 to most vertebrates; major cornua, now called ceratobranchial 

 I for the same reason. 



The retention of such terms as incus, even though it refers 



36 • OSTEOLOGY AND THE MAMMALIAN HEAD SKELETON 



