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Genus ACANTHYLLIS. 



Hirunclo apud Latham, Ind. Orn. Suppl. p. lvii (1801). 

 Acanthylis, Boie, Isis, 1826, p. 971. 



Chcetura apud Stephens in Shaw's Gen. Zool. xiii. pt. 2, p. 76 (1826). 

 Hirundapus apud Hodgson, J. As. Soc. Beng. v. p. 779 (1836). 

 Pallene apud Lesson, Compl. Buff. viii. p. 493 (1837). 

 Cypselus apud Delessert, Mag. Zool. 1840, Ois. pi. 20. 

 Hemiprocne apud Struebel, Isis, 1848, p. 362. 

 Acanthyllis apud Salvin, Gen. Index to Ibis (1879). 



The Spine-tailed Swifts, which differ chiefly from the common Swifts in having a short even tail 

 with the feathers tipped with sharp spines, inhabit the Palsearctic, Oriental, and Australian 

 Regions, only one species occurring, as a rare straggler, in the Western Palsearctic Region ; and 

 several species belonging to the very closely allied (if distinct) genus Chcetura inhabit the Nearctic 

 and Neotropical Regions. 



In general habits the species belonging to the present genus closely resemble Cypselus, but 

 they are even swifter on the wing, and are seldom seen to rest. They are said to construct 

 agglutinated nests in hollow trees, like the American Chimney-Swallow, and to lay elongated 

 white eggs. 



Acanthyllis caudacuta, the type of the genus, has the bill as in Cypselus, the wings very 

 long, narrow, and pointed, considerably exceeding the tail in length, the tail short, even, the 

 feathers terminated by long sharp spines ; the feet as in Cypselus, but rather stronger, the tarsus 

 bare in front and non-scutellate ; claws strong, large, curved, acute. 



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