FALCONIDJB DIURNAL RAPTORES. 443 



B. Wing more than 20 Inches ; inner webs of outer six primaries distinctly emarglnated. 

 a 1 . Tarsus densely feathered, all round, to the base of the toes. 



12. Aquila. Nostril narrowly oval, obliquely vertical. A very distinct web 

 between middle and outer toes. Feathers of the 1 nape distinctly lanceo- 

 late, 

 a*. Tarsus with lower part naked. 



& 1 . Tail short, much less than two thirds the pointed wing; feet moderately 

 robust, with upper half of tarsus feathered in front. Headcrestless; feathers 

 of neck all round, distinctly lanceolate. No distinct web between middle 

 and outer toes 



13. Haliaeetus. Tail rounded, of 12 rectrices. Upper outline of cere nearly 

 straight; nostrils with lower end rounded, opening rather abruptly in- 

 ward. 



14. Thalassoaetns. Tail cuneate, of 14 rectrices. Upper outline of cere 

 much arched ; nostrils with lower end pointed and beveled gradually to 

 the level of the cere. (Extralimital ; Kamtschatkan and Aleutian?) 



6*. Tail long, truncated, two thirds or more the very broad, rounded wing. 

 Feet enormously robust, with nearly the whole tarsus naked. Head with a 

 broad erectile crest of lengthened broad and rounded feathers; feathers of 

 neck all round, broad and rounded. A moderately developed web between 

 middle and outer toes. 



15. Thrasaetus. Secondaries greatly developed, both in length and breadth, 

 reaching to the end of primaries; fifth to seventh quills longest, the 

 outer seven with inner webs shallowly sinuated. Claws enormously 

 large and powerful, but rather obtuse, the inner and posterior ones 

 equal to their digits in length. (Extralimital; tropical.) 



GENUS ELANOIDES VIEILLOT. 



Elanoides VIEILLOT, Nouv. Diet. d'Hist. Nat. xxiv, 1818, 101. Type, Falco forftcatus LINN. 



Nauclerus AUCT. nee YIGOKS, 1825. 



CHAB. General external characters. Bill rather small and narrow, intermediate be- 

 tween that of Pandion and Elanus; compressed anteriorly, and very broad at the base; 

 the terminal hook well produced, the tomia very regular; cere ascending; nostril 

 broadly oval, oblique; gonys nearly straight; tomium of the lower mandible very con- 

 vex. Lores densely feathered, the feathers bristle-like. Feet robust; tarsus a little 

 longer than the middle toe, covered with large, irregular, hexagonal scales ; toes with 

 transverse scute llae nearly to the base; claws short, strong, abruptly flattened beneath, 

 the edges very sharp, the middle claw bent laterally, the inner side very convex, the pro- 

 jecting edge sharp and entire. No web between the toes. Primaries and rectrices ex- 

 cessively elongated and narrow, the former more than twice the length of the second- 

 aries. Outer tail-feathers about equal to the primaries, and more than twice as long as 

 the middle pair. 



Osteological characters* Cranium very similar in contour and proportions to that 

 of Pandion, but presenting important modifications in minor details. Superciliary 

 process of the lachrymal distinct from the frontal, which is completely anchylosed with 

 the nasal; inner convoluted edge of the palatines scarcely produced downward; nasal 

 septum completely ossified; pterygoid bone narrow, and of a uniform width throughout 

 its length. Sternum similar to that of Pandion, having, like it, a pair of indentations on 

 the posterior margin, and destitute of foramina; the clavicle, coracoids, and scapula are 

 also very similar. 



Anatomical characters. "Palate flat with two longitudinal ridges; upper mandible 

 with a tuberculate median ridge, lower deeply concave; posterior aperture of the nares 

 oblongolinear, with the edges papillate. Tongue somewhat decurved, emarginate, and 

 finely papillate at the base, flat above, its tip narrow and acutely emarginate. (Esopha- 



* Of this genus we have seen only the skull and sternum. 



