BLACK SKIMMER. 211 
the tendons, ¢, 6 twelfths in diameter. The intestine is 2 feet 4 inches 
long, its average diameter 23 twelfths. The rectum is 2 inches long. 
One of the cceea is 4, the other 3 twelfths, their diameter 1} twelfths. 
In another individual, the intestine is 22+ inches long; the coeca 5 
twelfths long, 1 twelfth in diameter; the rectum 1} inch long; the 
cloaca 9 twelfths in diameter. 
The trachea is 53 inches long, round, but not ossified, its diameter 
at the top 5 twelfths, contracting gradually to 24 twelfths. The late- 
ral or contractor muscles are small; the sterno-tracheal slender ; there 
is a pair of inferior laryngeals, going to the last ring of the trachea. 
The number of rings is 90, and a large inferior ring. The bronchi are 
of moderate length, but wider, their diameter being 34 twelfths at the 
upper part; the number of their half-rings about 18. 
The digestive organs of this bird are precisely similar to those of 
the Terns and smaller Gulls, to which it is also allied by many of its 
habits. 
