6. Inner side of left pterygoid plates, showing a large projecting 

 lower muscular tooth on the external pterygoid. 

 Fig. 7. Outer side of right external pterygoid, showing spina acces- 

 soria co-existing with a bridge across the foramen spino- 

 sum («'). 

 8. Ossified ligaments forming a thick prominent ridge, on the 

 outer and inner side of which are inlets into the oval and 

 spinal foramina, which in vertical section are T-shaped. 



PLATE 20. 



9. Ossified ligamentum pterygo-spinosum, showing a suture in 

 the ossified bridge, co-existing with a spina accessoria. 



10. Ossified ligamentum pterygo-spinosum accessorium, with a 



suture in the bridge of bone. 



11. Ossified ligamentum pterygo-spinosum accessorium, bridging 



over, and dividing the inlet into the foramen ovale into two 

 parts, spina angularis fi'ce, a back-directed spine from the 

 spina accessoria overlapping the foramen spinosum. 



12. Pterygoid processes from Chatham Island skull, showing the 



accessory outer pterygoid plate. 



13. Ossified ligamentum accessorium pterygo-spinosum, with no 



suture. 



14. Ligamenta pterygo-spinosum (p.s.) et accessorium («), show- 



ing their relation to the middle meningeal artery (m. m.), 

 and to the temporal nerves {t', t"). 



15. Ligaments in another specimen, showing their fusion at their 



pterygoid end. 



