PLATE XVIII. 



Respiratory Organs of Aptenodytes longirostris. 



(All the figures are of the natural size.) 



Fig. 1. — Cartilages of the upper larynx, seen from below. A. C. Anterior extremities 

 of the arytenoid cartilages. T. Trachea. T. C. Thyroid cartilage. 



Fig. 2. — Cartilages of the upper larynx, seen from above. A. C. Arytenoid cartilage. 

 C. C. Cricoid cartilage. T. Trachea. T. C. Thyroid cartilage. 



Fig. 3. — Cartilages of the upper larynx, lateral view. A. C. Arytenoid cartilage. 

 C. C. Cricoid cartilage. T. Trachea. T. C. Thyroid cartilage. 



Fig. 4. — Muscles of upper larynx. A. L. Apertor laryngis. L. P. Portion of laryngeal 

 pad. S. L. Sphincter laryngis. T. Trachea. 



Fig. 5. — -The upper larpix after removal of the sphincter laryngis. A. L. Apertor 

 laryngis. T. Trachea. T. C. Thyroid cartilage. 



Fig. 6. — Transverse section of trachea, showing the septum which divides the tube into 

 two passages. 



Fig. 7. — Tongue, upper larynx, and anterior portion of trachea ; ventral surface. C. H. 

 Cornu of hyoid bone. C. T. Cleido-thyroid muscle. C. Tr. Contractor 

 trachese muscle. T. H. Thyro-hyoid muscle. T. Tongue. Tr. Trachea. 



Fig. 8. — Posterior extremity of trachea, with the lower larynx and bronchi ; ventral 

 surface. B. Bronchus. C. Tv. Contractor tracheae muscle. L. Lung. 

 S. T. Sterno-trachealis muscle. 



Fig. 9. — Posterior extremity of trachea, with the lower larynx and bronchi; dorsal surface. 

 B. Bronchus. C. Tr. Contractor tracheae muscle. L. Lung. 



Fie. 10. — Framework of lower larvnx. 



