REPORT ON THE ANATOMY OF THE PETRELS. 37 
Aeipetes antarcticus (figs. 20, 21), commonly placed in the genus Thalasswca with 
Kailua) 
QO ! 
OO: 
Fic. 17.—Syrinx of Ossifraga gigantea, Fic. 18.—The same, Fic. 19.—a, b,c, sections of syrinx and trachea 
from before. from behind. of Ossifraga along the lines a, 3, c, of fig. 
17, to show the double nature of the 
tracheal tube below, and its complete 
division by a median septum above. d, 
trachea opened from the side, to show the 
median septum, dividing it into two paral- 
lel tubes, through the left of which a 
pointer is passed, below, and terminating 
above by a free margin. 
Thalasseca glacialoides, completely differs in the structure of its syrinx from the last 
three species described, and is more like Prion. The two first pairs of bronchial rings 
Fic. 20.—Syrinx of Aeipetes antarcticus, from before. Fic, 21.—The same, from behind. The smaller figure 
represents a section of the trachea, to show the 
a imperfect septum dividing it. 
ave complete anteriorly, the second being ossified, for a small extent only, in the middle 
