BIBDS OF NORTH AND MIDDLE AMEBICA. 597 



iws. Even in the character of the bill and feet, however, the 

 semblance is largely a superficial one, and when a close examination 

 made many constant differences become obvious in the structural 

 tails of the bill and feet in the two groups. Thus in the Striges the 

 ixillar tocnium is never notched, toothed, nor lobed; the "cere" is 

 very different character, consisting, in reality, of the usual mem- 

 ane covering the unperforated part of the nasal fossae, continued 

 ross the mesorinal portion of the cuhnen, the so-called cere being 

 us wholly post- and supra-nasal, usually with the lateral (post- or 

 ■cum-nasal) portion more or less inflated. It is in the structure of 

 e feet, however, that the greatest difference is observable. 

 "The structure of the feet and more particularly the toes of owls is 

 ry peculiar. When perching, the arrangement of the toes is zygo- 

 ,ctyl; that is, two in front and two behind,'' but when an owl pounces 

 ion its prey, the four toes point to the four quarters of a circle. 

 ;ain, when the bird alights upon the ground, the arrangement is 

 11 different, being more like that of a typically avian foot — three 

 es in front and one behind. This facile adjustment to different 

 nditions makes the foot of great efficiency in all its functions." * 

 single member of the Accipitres, the genus Pandion, "shares the 

 ^ital elasticity of the owls," and also, alone in that order, possesses 

 e bony tarsal ring or loop, a character evidently correlated with the 

 ^ital manipulation. 



The following special papers pertaining to the structure and classi- 

 ation of owls are commended to those who desire further inf orma- 

 m on the subject: 



LLETT, Robert. — Craniets og Oreaabningemes Bygning hos de nordeuropaeiske 

 Arter af Familien Strigidse. 



An Englisli translation edited and annotated by Dr. R. W. Shufeldt was pub- 

 lished in the Journal of Morphology, xvii, 1900, 119-176, pis. 15-20+7 text cuts, 

 under the title "Professor CoUett on the Morphology of the Cranium and the 

 Auricular Openings of the North-European species of the Family Strigidae," the 

 illustrations from the original paper. 



4.RK, Hubert Lyman. — The Pterylography of certain American Goatsuckers and 

 Owls. Proc. U. S. Nat. Mus., xvii, no. 1018, 1895, 551-572; 11 cuts in text. (Owls 

 treated on pp. 559-566, a key to the genera, based on pterylographical characters 

 alone, being given on p. 560.) 



CRAW, W. P. — A Contribution toward our Knowledge of the Morphology of the 

 Owls. Trans. Linn. Soc, 2d ser., Zool., vii, 1898, 223-275, pis. 24-29. 



CRAiT, W. P.— On the Pterylography of Photodilus. The Ibis, Jan., 1903, 36-48, 

 pi. 2; 6 cuts in text. (Includes a "Revised Key to the Subfamilies and Genera 

 of the Family Asionidse, " on pp. 47, 48.) 



EBB, C. William. — Owls of the Nearctic Region. Reprinted from the Eleventh 

 Annual Report of the New York Zoological Society. Pp. 38, 1 full-page (frontis- 

 piece) and 15 text cuts, all reproduced from photographs. (1907.) 



■ This is not strictly correct, for when perching the outer toe usually stands nearly 

 right angles with the middle toe and hallux, though often inclined more back- 

 rd than forward. 

 ' Beebe: Owls of the Nearctic Region, p. 11 



