68 



CORY'S GANNET. 



The l)ron(:lilalis is represented by thin, strap-like muscles, seen in Fig. 14, e e. Fig. lS,e e, and Fig. 17 

 E, e. These muscles extend from the base of the sterno trachealis to the first laryngeal half ring, and their 

 function is to render tense the laryngeal vibrating membrane seen at u. Fig. 17, E. 



The tympaniform membranes. Fig. U, p p, ai-e long and wide, occupying the entire length and width 

 .if the bronchial tubes, the outside one of which is given in Fig. 17, E, b, and there is a much less prominent 

 membranous muscles connecting the tubes than in Sula bassana. 



The OS transversale is present, but there is not even the rudiments of a semiluna membrane, as seen in 

 the Common Gannct, while there is a shield-like projection of the larynx over the lower side of the division 

 of the bronchial tubes, compare to. Fig. C>, A. with o. Figs. U and 18 ; nor do the tubes narrow as much 

 at the laryngeal termination as in Sula bassana; see Fig. 7, 0, and compare with Fig. 1 S, o e e. The 

 larger viljrating surface of the tympaniform membranes of Cory's Gannet, compared with that of the Com- 

 mon Gannet, the Liryngeal vibrating membranes being the same, and counting out the mere rudiment of the 

 semiluna seen in tlie Common Gannet, as this is without doubt functionless, should give to this species a 

 greater power of voice. In fact, such is the case, and I have heard Cory's Gannet give more notes than I 

 ever heard the Common Gannet utter, but the cries of both are very harsh and discordant. 



In Cory's Gannet, as remarked, there is no indication whatever, of the singular gland which I have 

 called the thymus, adhering to the larynx, but there is a rudimentary thyroid present attached to the sin- 

 gle carotid arterj'. This is a small elliptical body, about .2.j long and lies on the inside of the carotid, the 

 left of which only is developed; see Fig. 18, a being the carotid artery, c, the thyroid gland, h, the heart, n, 

 w, X, and z, other arteries. The thyroid is quite likely functionless, or nearly so ; 1 judge this to be a fact 



Fig. 19. 



Head of Cory's Gannet, Sula coryi, adult male in white phase of plumage ; taken on Little Cayman, 

 May 2d, 1888 ; type. 



as the gland is of such a small size. In a young Great Blue Heron, but fully grown, that I have recejitly 

 dissected, 1 found two thyroids one adhering to each carotid artery, but the left thyroid was nearly twice 

 the size of the right, and in it I found some well developed, cylindrical glands, each of which was fastened 

 by its inner, terminal extremity to the outside of a small vessel, not a branch of the carotid, that passed 

 through the gland. The right thyroid in this bird also had a small blood vessel passing through it. but I 

 could find no developed glands. 



In the only specimen of the Booby Gannet that has come into my hands to dissect. I find that I have 

 made no notes nor drawings of the appearance of the tongue nor superior larynx. It may be possible that 

 these organs were missing from the body that was kindly given to me by the Bangs Brothers of Boston, 

 who obtained the Ijird, a young male, in the Quincy Market, where they were informed that it was taken 

 on Cape Cod. 



Color. Adult. White Phase. Primaries, first rowof coverts, spurious wing, exposed portion of 

 secondaries, and nii.ldle wing coverts, dai-k limwn, remainder of plumage tinged with creamy, which on top of 



