74 



BLACK SKIMMER. 



liver equal, 1^ inches long. 

 twelfths broad. 



The heart of moderate size, ly 1 ^ long, 10 



The oesophagus, of which only the lower portion, 

 a, is seen in the figure, is 8 inches long, gradually 

 contracts from a diameter of 1 inch to 4 twelfths, 

 then enlarges until opposite the liver, where its 

 greatest diameter is 1 T \. Its external transverse 

 fibres are very distinct, as are the internal longitu- 

 dinal. The proventriculus, b, is 9 twelfths long, 

 its glandules extremely small and numerous, round- 

 ish, scarcely a quarter of a twelfth in length. The 

 stomach, c, d, e, is rather small, oblong, 1 inch 4 

 twelfths long, 11 twelfths broad, muscular, with the 

 lateral muscles moderate. The cuticular lining of 

 the stomach is disposed in nine broad longitudinal 

 rugae of a light red colour, as in the smaller Gulls 

 and Terns. Its lateral muscles are about 4 twelfths 

 thick, the tendons, e, 6 twelfths in diameter. The 

 intestine is 2 feet 4 inches long, its average diame- 

 ter 2j twelfths. The rectum is 2 inches long. 

 One of the coeca is 4, the other 3 twelfths, their 

 diameter li twelfths. 

 In another individual, the intestine is 22 i inches long; the coeca 5 twelfths 

 long, 1 twelfth in diameter; the rectum l| inches long; the cloaca 9 twelfths 

 in diameter. 



The trachea is 5| inches long, round, but not ossified, its diameter at the 

 top 5 twelfths, contracting gradually to 2\ twelfths. The lateral or con- 

 tractor 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 o\ 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. 



