176 



THE VERTEBRATE SKELETON. 



sphenethmoid encircling the anterior end of the brain, its place 

 being partly taken by a pair of orbitosphenoids, (4) there is no 

 definite tympanic cavity. 



20' 



21 



FIG. 27. 



10. 

 11. 



DOKSAL VIEW OF THE SKULL OF A LiABYBINTHODONT (CupitO- 



saurus nasutus)x% (from VON ZITTEL). 



premaxilla. 12. postorbital. 



nasal. 13. 



maxilla. 14. 



anterior nares. 15. 



frontal. 16. 



prefrontal. 17. 



lachrymal. 18. 



jugal. 19. 



orbit. . 20. 



parietal. 21. 

 postfrontal. 



interparietal foramen. 



squamosal. 



supratemporal. 



quadrato jugal. 



quadrate. 



epi-otic. 



dermo-supra-occipital. 



exoccipital. 



foramen magnum. 



LABYRINTHODONTIA. The skull in Labyrinthodontia is re- 

 markable for its extreme solidity, the large number of bones 

 which are present, and the extent to which the roofing over of 



