84 DEVELOPMENT OF THE SKELETON OF THE TUATARA. 



PLATE V. 



SPHENODON PUNCTATUS. THE QUADRATE, HTOID, AND COLUMELLA AURIS. 



an., angular; b., boundary between stapes and extrastapedial cartilage; b.a., branchial arch; 

 b.c., branchial cleft ; c. 1 ", horizontal semicircular canal ; ca. } carotid artery ; ca. r , branch of carotid 

 artery; c.au., auditory capsule ; e.c., extrastapedial cartilage; eu., eustachian recess; fe., fenestra 

 in suprastapedial cartilage ; h. 1 , anterior cornu of the hyoid ; j.v., jugular vein ; mk. } Meckel's 

 cartilage; mt., mouth; n. v.-xi., cranial nerves; n.vii.', branch of chorda tympani; ph., pharynx; 

 p-p., parotic process; pq., pterygoquadrate ; q., quadrate; q.' t otic process of quadrate; s.a., supra- 

 angular ; sg.', anterior process of squamosal ; sq.", posterior process of squamosal ; s.st., supra- 

 stapedial cartilage ; st., columella (stapes) ; st.', boundary between columella and extrastapedial 

 cartilage. 



Figs. 15. Stage P. A series of sections, in order from within outwards, showing the primary 

 relationships of the columella auris to the hyoid and quadrate. X 40. 



Fig. 1. Represents the most internal section No. 1. 



Fig. 2. Represents section No. 6. 



Fig. 3. No. 8. 



Fig. 4. No. 19. 



Fig. 5. No. 27. 



Fig. 6-11. Staff e Q. A similar series to the above. X 25. 



Fig. 6. Represents the most internal section No. 1. 



Fig. 7. Represents section No. 11. 



Fig. 8. No. 26. 



Fig. 9. No. 36. 



Fig. 10. No. 46. 



Fig. 11. No. 57. 



Fig. 12. Stage R. Transverse section of auditory region passing through quadrate and columella 



auris. x 25. 



Figs. 13-14. Stage S. Sections, in the same order as figs. 1-5, showing the relation of the 



suprastapedial cartilage to the quadrate. x 20. 



Fig. 13. Represents the more internal section No. 1. 



Fig. 14. Represents section No. 16. 



