54 PTERYLOGRAPHY. 



1. Falcons with the pectoral stem of the inferior tract undivided. 



a. With the posterior portion of the spinal tract of uniform breadth and furcate 



anteriorly. 



The representative of this remarkable combination, which is so extremely similar to the 



Vulturine type, is the Falco ecaudahis DAUD. (Le Bateleur, LE VAILL. Ois. d'Afrique, I, pi. 7 



and 8), of which Lesson has formed the subgenus Theratopius. I have also to mention, with 



regard to the pterylography of this very singular bird, that the inner branch at the extremity of 



the jugular portion of the inferior tract is very distinct, that the union of the jugular with the 



pectoral portion consists of a single row of feathers, and that the lumbar tract appears to be 



deficient. The two arms of the scapular part of the spinal tract are remarkably long, as'they 



project beyond the apices of the scapulae. The dorsal portion reaches nearly to these arms, and 



divides only into two very short, diverging rows of feathers, which unite themselves to the arms 



of the fork. The number of remiges is thirty-three, a perfectly enormous number for a Falcon : 



the first is, perhaps, the longest, but I must leave this uncertain, as it was in process of growth, 



otherwise certainly the second : the third is a little shorter, and the remainder to the tenth 



rapidly diminish. The first five have an emargination on both halves of the vane ; this is but 



slight on the outer one, but on the inner it forms a very acute angle, and commences near the 



middle of the length of the feather. By this means the second half is rendered very narrow and 



acute. Tail very short, scarcely one fourth the length of the portion of the folded wings which 



projects over it. 



In other particulars of its structure this bird approaches the Buzzards ; but it has the feet 

 entirely covered with scales, and with only one or two scutes upon the backs of the toes imme- 

 diately above the base of the claws ; likewise a remarkable analogy with the Vulturine type. 



b. With the posterior part of the spinal tract deeply divided, and dilated externally on 

 each arm. 



FALCO (PANDION) fialiaetos. (Plate II, fig. 7.) 



This Hawk, which is so remarkable in many respects, does not present only the two peculiar 

 characters already indicated, but it differs pterylographically in many other points from the rest 

 of its associates. These differences are as follows : 



1. The contour-feathers have no aftersJiaft, and are generally very small and short; indeed, 

 smaller than in any other Falcon. Hence the legs present no appearance of breeches, and the 

 trunk seems very small in comparison with the wings and legs. The feathers of the inferior 

 tract are the smallest of all. 1 



2. The inferior tract divides close to the throat, and its two arms separate considerably. la 

 the vicinity of the furcula they become dilated, but form no interior branch ; they pass uninter- 

 ruptedly and constantly becoming broader upon the pectoral muscles, of which they occupy the 

 whole of the middle surface, continue backwards at an equal distance from the crest of the 



1 The absence of the aftershaft causes this Falcon to approach the Owls as much pterylogra- 

 phieally as it does zoologically in the reversible toe, and anatomically in the non-pneumatic femora and 

 the completely closed osseous canal on the os metatarsi for the passage of the sinew of the extensor 

 digitorum communis. 



