Studies on Avian Anatomy. — II. 
35 
It appears from comparison of the structures mentioned that 
Phalaenoptilus and Aeronautes go together, and Bubo and Geococ- 
cyx . The relation, however, is less close between the two former 
than between the two latter. The question of the relationship of the 
Caprimulgi, however, is not one to be settled by the examination of 
a few genera, but requires a more careful and thorough investiga- 
tion of many related forms than has yet been made. 
It is interesting to note here that Phalaenoptilus is probably the 
most primitive of these four genera. The elongated brain and its 
relatively small size compared with the head, the fairly well developed 
right oviduct, and the downy plumage of the young are facts which 
indicate it as the most primitive. 
Bibliography of the Anatomy of Geococcyx, Bubo, and Aeronautes . 
(Exclusive of the Osteology.) 
Beddard, F. E. 
1888. On the Classification of the Striges. Ibis. 
1898. The Structure and Classification of Birds. London. 
Clark, H. L. 
1894. The Pterylography of Certain American Goatsuckers and 
Owls. Proc. U. S. Nat. Mus. 
1901.- The Pterylosis of Podargus: With notes on the Ptery- 
lography of Caprimulgi. Auk. 
