SKULL — MAMMALS 



187 



Distinct occipitalia often persist in the adult, but as often all fuse 

 to a single occipital bone with which the interparietal (scarcely 

 known elsewhere above primitive reptiles) may unite. This occip- 



Frc 199. — Ventral views of developing cranium of Orycteropus (W. K. Parker, '84), 

 A, with most of the membrane bones removed; B, membrane bones in place; cartilage 

 stippled, als, alisphenoid; bo, basioccipital; bs, basisphenoid; c, condyle; e, ethmoid 

 cartilage;/, frontal; g, mandibular fossa; m, maxilla; oc, otic capsule; os, orbitosphenoid; 

 pc, paraseptal cartilage; pg, pterygoid; pi, palatine; pm, premaxilla; pp, parotic process; 

 ps, presphenoid; sh, stylohyoid; so, supraoccipital; sq, squamosal; t, tympanic; v, vomer; 

 s, zygomatic; V-XII, nerves. 



ital surrounds the foramen magnum which is nearly vertical in 

 primitive orders (rodents, bats, some insectivores), but is usually 



