HIRUNDAPUS. 
appreciabty from Cypseloides in the length of the tail, and I separate these 
as a new genus 
Ch^turellus, 
naming Hirundo rutula Vieillot as type Ghceturellus rutilus. Previous to 
Hartert’s reference of these to Cypseloides they had been classed in Ghoetura, 
and this indicates the nature of the tail. It is quite intermediate between 
the two genera, while the coloration is unique. 
The name Cypseloides appears to be in a somewhat precarious position, 
as it seems to have been proposed as a substitute for “ Hemiprocne sensu 
strictu ” and to have been dubiously put forward by Sclater in 1865. Streubel 
in the same place {Isis, 1848, col. 366) wrote : “ Senes seu Hemiprocne 
proprie dictu,” but I have not noted Senes cited as a generic name. I do 
not propose to discuss this item, but point out that there is an alternative, 
Acanthylops Gray, 1869, which has for type H. fumigata Streubel, herewith 
designated. Richmond {Proc. U.S. Nat. Mus., Vol. LIII., p. 674, 1917) has 
stated tLat “ Aclmntylops Bonaparte 1857,” is a nomen nudum. 
There is, therefore, in America a series of Spine-tailed Swifts and also a 
series of semi-Spine-tails : the latter show very clearly the evolution of the 
spine-tail and, moreover, indicate in no uncertain manner its appearance in 
independent groups. The whole of the Micropodidm have structural features 
as regards the external appearance of the bill, the formation of the wing and 
the structure of the feet of a generalised nature. In the first named the 
position of the nostrils may prove a good character when the skull is examined, 
as it suggests different structure internally. The wing shows little variation, 
the length of the primaries varying in proportion to the secondaries, while 
sometimes the first, sometimes the second primary is longest. The feet are 
small, and the differences consist in the position of the toes and the feathering 
or absence of feathers on the tarsus. Anatomical investigation has proved 
that these superficial features are correlated with important internal differences. 
The tail formation which is here used seems quite as important a feature 
as the others, when it is criticised from its nature, not its apparent form only. 
This reviev/ was undertaken to determine the validity of the genus 
Hirundapus, and as this is the earliest name given to the large Spine-tailed 
Swifts and, moreover, introduced for a bird certainly congeneric with tlie 
Australian form, it is indisputable. From it, however, must be divorced 
the diverse species classed by Hartert under the name Ghcetui'a and these 
must be separated into many genera or subgenera. 
Thus, to recapitulate, the Hirundapine forms are divisible into three 
genera, Hirundapus, Pallenia and Streptoprocne. The smaller species into many 
genera, Chmtura for the American forms, Telacantkura, Neafrapus and Alterapus 
