66 PTERYLOGRAPHY. 



graduated. Their proportions cannot be accurately stated, as they were in moult in the specimen 

 examined, but the third is probably the longest. This and the two preceding have a deeply 

 seated, imperfect emargination. 



12. DIPLODON. 



Under this name I separate as a distinct group two species referred by Cuvier and Tem- 

 minck to the True Falcons ; x they no more belong to the True Falcons than does the preceding. 

 Unfortunately, I have been able to examine carefully only one species, F. bidentatus LATH. 

 (TEMM., PL Col., 38) ; and I refer the second, F. diodon TEMM., PL CoL, 198, to this position 

 solely from its external similarity. Pterylographically, however, F. bidentatus agrees perfectly 

 with F. lop/totes, but the outer branch of the inferior tract is still further united to the stem than in 

 that species. The dorsal portion of the spinal tract remains far from the scapular part, and has no 

 rows of feathers beside it. The powder- down- tracts extend forwards in the shape of narrow bands to 

 the shoulders. Of remiges I counted twenty-three ; the first was as long as the ninth; the second 

 and third were in process of growth ; the fourth considerably longer than the fifth, so that it or 

 the third is the longest. The emargination of the first primary is so slight that it may almost be 

 said not to exist. 



13. CIRCUS. 



The species of this group examined by me, namely, F. pygargus, F. ceruginosus, and F. cine- 

 rarius, agree in all the characters of their pterylosis with Milvus, Pernis, and Astur, especially in 

 the narrow form of the tracts, the condition of the dorsal portion of the spinal tract, the smallness 

 of the lumbar tract, and the shortness of the inner branch of the inferior tract ; and differ from 

 them chiefly in the oblique position of the outer branch of the inferior tract, which does not run 

 parallel to the main stem, and is therefore rather more connected with it anteriorly than in the 

 above-mentioned Falcons. This difference is increased by a distinct oval space in front of the ear 

 and beneath the eye, which I met with at least in F. pygargus ; but the Harriers may be with 

 most certainty distinguished as a form differing at least from all other European Falcons by the 

 powder-down-tracts which ascend on each side of the dorsal portion of the spinal tract as far as 

 the shoulders. In the acute and narrow wings I found twenty-four and twenty-five remiges, of 

 which the first is equal to the sixth or seventh, the second not quite equal to the fifth, and the 

 third is either of the same length as the fourth or does not quite equal it. The four last men- 

 tioned have a very imperfect angular emargination, and a corresponding diminution of the inner 

 vane. 



In conclusion, I may notice the nest-plumage of the Diurnal Rapacious Birds, which I have 

 carefully investigated, especially in Fdlco aruyinosus and F.palumbarius. It consists, as usual 

 (see p. 14), of downy barbs, which are attached to the first perfect barbs of all the contour- 

 feathers, even the remiges and rectrices, and disappear as the bird becomes fledged. More- 



1 The group had been previously named Harpagus by Vigors in 1824. P. L. S. 



