386 Mr. Vigors's Sketches in Ornithology* 



supporting their evolutions, and directing their progress, as they 

 soar or sail through the air. From these considerations I shall 

 venture to characterize the group as follows under the generick 

 name of 



Naucleuus. 



Rostrum subbreve, debile, compressum; naribus subovalibus, 

 in ceromate, setis ad basin instructo, oblique positis. 



Alee longaj ; remige 2d4 aut 3tia longissima. 



Cauda longa, maxime furcata. 



Pedes breVes, debiles ; tarsis reticulatis ; acrotarsiis infra genu 

 usque ad medium plumosis ; unguibus hand cylindricis. 



Corpus gracile, concinnum. 



It will of course be immediately evident that the nearest affinity 

 of this genus in the Milvine subfamily is to Elanus; with which it 

 has the characters of the bill and legs in common, the cylindrical 

 ungues of the latter being excepted. There is also a general simi- 

 larity in the colours of the two genera, and in the disposition of 

 them. Nauclerus is distinguished from the true Milvus by the 

 greater developement of the character of the forked tail ; by the 

 relative proportions of the wing feathers, the fourth being the 

 longest in Milvus; and by the reticulation of the acrotarsia^ those 

 of Milvus being covered with even scales or scutellated. Although 

 the species known at present of this new group have been already 

 well described, the following specifick characters taken immedi- 

 ately from two fine and apparently adult specimens now before me 

 may not be unacceptable. 



* Remige ^dd longissima. 

 RiocouRii. N. albus, capite colloque superne, dorso alis rectri- 

 cibusque griseiSy lined ante poneque oculos maculdque alarum 

 nigris. 



Rostrum nigrum: cera pedesqne flavi. Remiges superiores 

 griseae, interne ad basin alba?, tribus exterioribus exceptis, apice 

 albo-marginatae ; secundariae quatuor internae nigrae, maculam 

 longitudinalem nigrum formantes : inferiores albae apice griseae ; 

 ptilis inferioribus partim nigris, maculam longitudinalem nigram 



