ANATOMY OF THE OPHIDIA, 395 
and grooved on the anterior quadrant. There are 9 large palatine 
teeth which are grooved on the external quadrant. There are 21 
pterygoid teeth, about one half the size of the palatine teeth and 
grooved on the internal quadrant. There are 23 mandibular 
teeth which are grooved on the external quadrant. 
Specimen.—California Acad. Sci. No. 15309. Caloocan, Luzon, 
Philippine Islands. Adult male. 
The tracheal membrane begins at the glottis and lies along the 
right side of the tube; at the 9th g. it is 1 mm. wide and at the 
17th g. it is 2 mm. wide and begins to be lined with air-cells; 
at the 44th g. it has increased until it forms three-fourths of the 
circumference of the trachea; towards the base of the heart it 
decreases somewhat in size and merges with the lung. The 
respiratory tissue lining the tracheal membrane is of a specialized 
type, the individual air-cells being from three to four times deeper 
than wide. When the cartilaginous portion is laid open the 
lumen appears to be but 2 mm. in diameter; to the left may be 
seen the openings of the air-cells, which are in longitudinal rows. 
The cartilages lie at first on the right and beyond the 4th g. on 
the ventral side of the tube. The trachea ends abruptly at the 
54th g., and there is not a trace of an intrapulmonary bronchus. 
The right lung terminates at the 94th g., which is the same level 
as the end of the liver. The posterior extremity is free and 
rounded as in the Boine type, and not bound to the parieties ; 
upon opening the ccelum it may be seen just posterior to the end 
of the right lobe and to the right side of the left lobe of the 
liver. The lung is lined with air-cells throughout, but towards 
the end they become shallow and irregular. There is a free apex, 
2mm. long, on the right of the trachea, and extending to the 
52nd g. The left lung is completely suppressed. 
The heart is located rather to the rear, being in terms of 
gastrosteges 33 per cent. down the vertebral column, in Colu- 
brine snakes the prevailing position is about 25 per cent. The 
liver is divided by an incisure along the ventral surface into 
right and left lobes; the right lobe begins at the 68th and ends 
at the 92nd g. 
The pulmonary artery divides into two equal branches opposite 
the 5lst g. The anterior is distributed to the trachea, the 
posterior to the lung. The branch to the lung divides just before 
the tip of the apex of the lung into dorsal and ventral branches. 
The vertebral artery arises from the right aortic arch at the 
48th g.and runs superficially to the 14th g.; just before dis- 
appearing it sends a minute twig forward to the next inter- 
vertebral space. It gives off 23 intercostal branches which enter 
in the median line; the gastrostege level at which they enter the 
parieties is as follows:—I. arises just at the origin of the ver- 
tebral and courses alongside of it to the level of the 45th g.; 
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