ANATOMY OF THE orniDiA. 421 



G.istrasteges 227, tlie last shield divide:!. Anal entire. 

 Urosteges 120 pairs. Supvalabials 10 ; the fifth to the seventh 

 entering the eye ; on the right the fourth is reduced and fused 

 with the posterior inferior angle of the third. Infralabials 10 on 

 the left, 11 on the right, the a Iditional shield is between the 

 corresponding third and fourth. Anterior geneials larger than 

 the posterior, the right in contact with four and the left with 

 five infralabials. Gular shields in six pairs. 



Anatomy. — -Maxillary bone with 20 teeth, the posterior three 

 with a bi'oad shallow groove ; the five preceding these are 

 also grooved but less distinctly. Palatine bone with 8 teeth, 

 increasing in size posterioidy ; the anterior tip of the bone 

 reaches to the interval between the second and third maxillary 

 teeth. Pterygoid bone with 28 teeth. Dentary bone with 

 18 teeth, the anterior enlarged and grooved on the external 

 quadrant. 



In terms of gastrosteges the external landmarks of the viscera 

 are as follows : — 



Total number of gastrosteges 227 100 p. cent. 



Apex of heart 58 25-6 



Liver, anterior tip 73 32-2 



„ posterior end 112 49-4 



Gall-bladder, centre 232 58-2 



Kidney, right, anterior tip 183 80-8 



,, ,, posterior end 201 89 



„ left, anterior tip 196 86'5 



,, ,, posterior end 214 94-2 



Ileo-cfBcal valve 209 92-2 



Vaginal cornua, base 216 95 



The cartilaginous rings of the trachea are complete from the 

 glottis to the angle of the jaw ; from this to their termination 

 on the ventral surface of the lung, at the apex of the heart, they 

 are interrupted. The tracheal membrane begins with the semi- 

 rings ; it is on the right side of the tube, and is continued caudad 

 to the base of the heart. For the greater part of its length it 

 comprises more than half the circumference of the tube. At 

 its termination it becomes continuous with the pulmonaiy pleura. 

 The elasticity of the rings maintains their free ends in close 

 apposition, and the membrane lies in a lax state by the side of 

 the trachea. When the windpipe is dilated, the ends of the 

 rings are separated and the tracheal membrane becomes a 

 functioning part of the organ. Under ordinary conditions the 

 air passes only through that part of the tube that is formed by 

 the semi-rings. Anteriorly the pulmonary tissue begins at the 

 level of the auriculo-ventricular septum. In the lung it is 

 confined strictly to the dorsal half of the circumference. 

 Posteriorly it is drawn out as a fine streak from which ai'e sent 

 out transverse septa ; it terminates on the left side of the air-sac, 

 at the level of the 79th ventral. Posteriorly the lung is continued 

 as a membranous air-sac ; exactly where it ends cannot be 



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