Some Considerations respecting the Parietal Bone. 



335 



between the exit of the optics and tergeminal nerves, or the}' may 

 partially or entirely enclose the latter (Parker). 



The parietal touches the sphenoid in Cystophora, Hyaena, Ursus 

 polaris, Hyrax, Dugong-, Kangaroo, Lemur, Canis, Felis ,' Prosimia, 

 Galago, Loris gracilis (by a point), Nyticebus, Lepidolemur, Propithecus, 

 Indris, Chiromys, Hapale, Pithecia, Lagothrix, Cebus, Mycetes, Cerco- 

 pithecus (sometimes), Macacus rhesus (some), Semnopithecus entellus 

 (some), Orang (mostly ace. to Flower), Gorilla and Troglodytes some- 

 times, Hylobates hainanus. The parietal usually articulates with the 

 sphenoid in Homo and the suture is sometimes long (2 — 3 cifï long). 

 A cercopithecus is figured hy Owen, which has a Parieto-sphenoidal 

 suture on the left side but not on the right. 



Fig. 39. 

 Simia Satyrus. 



Fig. 40. 

 Gorilla (Manchester). 



Loris gracilis, semnopithecus leucoprjinnus Gorilla (?) and Homo 

 have sometimes a very much reduced parieto-sphenoidal fissure. 



The influence of confinement and climate, as well as food, may 

 tend to produce wormian bones and these may unite to one of the 

 bones abutting on the fontanelles thus giving rise to seeming natural 

 varieties. Some varieties must be studied in the light of other facts 

 such as wormian bones being found elsewhere in the same skull. It 

 may also be stated that collectors have found considerable variations 

 in the same species. 



An interesting variety occurs also in some x\merican Monkeys 

 and in Hylobates Mülleri. Namely an articulation between the 

 parietal and jugal. 



