THREE UNPUBLISHED PAPERS BY BLYTH. 309 



B. With less robust feet, the representative of the hind toe 

 rotating backwards, and opposable to the other toes. 



Genus Acanthyllis, Boie. (Spiny-tailed Swifts). 

 Distinguished by robust general conformation (as in Cypselus), 

 and by having an even or wedge-shaped tail, with the shafts of 

 the feathers prolonged into rigid spines, more or less developed. 

 The tarsi are covered with a naked skin, and with the toes are less 

 robust than in Cypselus, and comparatively somewhat elongated. * 

 About fifteen species are known, which severally inhabit S.E. 

 Asia and its islands, Australia, Africa, and both Americas.! 

 Two only, of small size, visit N. America, one on either side of 

 the great mountain range ; and that of the Atlantic States has 

 been the most studied of the genus. This bird is known as the 



* In Mr. Gosse's 'Birds of Jamaica,' an extract from the MS. notes of 

 Dr. Anthony Eobinson (vide the work cited, p. 20) is given in the notice of 

 a rather large species, supposed to be A. collaris (Pr. Max.), in which it is 

 stated — "As tliis bird seldom alights, it is furnished with two supernumerary- 

 bones, which are placed on the superior and exterior part of the leg [tarsus?] ; 

 the skin that covers them is of an obscure flesh-coloiir ; they are of an oblong 

 ovated form, \ in. long ; and as the bird hangs upon a wall, rock, &c., by its 

 claws, these bones are pressed close to it, and the leg thereby secured from 

 harm." The two large Indian species have no trace of such a structm-e. 

 Of the same species another observer remarks — " The legs are curiously con- 

 structed : the tarsus cannot extend fm-ther than at an angle of 28°, nor can 

 it be straightened ; so that it corresponds with the tail-feathers, and keeps 

 the bird in an upright position against vertical rocks and trees. From this 

 formation the bird cannot stand erect on the ground, nor can it apparently 

 walk " ; and the same observer was told by fishermen and others that they 

 have taken young ones clinging to the vertical honeycomb rocks, agaiut 

 whose base the sea dashes. Dr. Eobinson, however, remarked of a livin^ 

 specimen that on the floor "it crept along with its legs bent, leaning on the 

 aforesaid bones, but was not able to raise itself upon its feet. When by any 

 accident this bird falls to the ground, as sometimes happens, it creeps or 

 scrambles to some rock or shrub, when, bending the tail and expandin<T its 

 wings, it elevates its body, and at the same time throwing its lec^s forward 

 catches hold of the rock, &c., with its claws, and climbing u^ to a proper 

 height throws itself back and recovers its wings." This species has been 

 traced to caverns in the mountains of Jamaica, in which they appear to 

 nestle by hundreds. In Cypselus and Collocalia it may be remarked that 

 the action of both the tibial and tarsal joints is particularly free. 



I A single individual of the Himalayan species has been killed in England 

 at or near Colchester, in Essex, as I am informed by Mr. Bartlett. [A second 

 has since been procured, cf. Zool. 1880, p. 81. — Ed.] 



