1865.] GENERA AND SPECIES OF CYPSELIDZ. 597 
This very remarkable peculiarity in the foot of the typical Cypse- 
lide, together with the abnormal position of the hallex or posterior 
digit, which is either placed anteriorly in a line with the other digits 
or more or less laterally, serves to divide the family Cypselid@ into 
two distinct subfamilies. 
a, CypsELIN2—tarsis plumosis: digitorum externi et medii pha- 
langibus utriusque tribus: hallice antice vel lateraliter versa. 
6. CoaTurinam—tarsis nudis: digitorum phalangibus, quoad 
numerum, normalibus : hallice postice posita, interdum versatili. 
The Cypseline contain two genera, which may be separated by 
the following diagnoses :— 
1. Cypselus: tarsis plumosis, digitis nudis: hallice antica. 
2. Panyptila: tarsis digitisque plumosis: hallice laterali. 
The Cheturine appear to embrace four well-marked genera, 
which may be shortly diagnosed as follows :— 
a, tarsis digito medio longioribus. 
a', rectricibus spinosis. 
a", rachidum apicibus prominentibus, (1) Chetura. 
6", rach. apicibus non prominentibus, (2) Cypseloides. 
b!, rectricibus non spinosis ............ (3) Collocalia. 
6, tarsis digito medio brevioribus .......... (4) Dendrochelidon. 
Oue of the most remarkable points in the structure of the Cypse- 
lide is the great development of the salivary glands. In all the 
species of which the nidification is known, the secretion thus pro- 
duced is used more or less in the construction of the nest. In most 
cases it forms a glue by which the other materials are joined together, 
and the whole nest affixed to the rock, wall, or other object against 
which it is placed. In some species of Collocalia, however, the 
whole nest is made up of inspissated saliva*, and becomes the edible 
bird’s-nest so well known in the East. 
The eggs of the Cypselide appear to be always regularly oval in 
shape, and colourless. 
’ Subfam. I. Cypsreninz. 
Genus 1. CypsEexus. 
Apus, Scopoli, Intr. Nat. Hist. p. 483 (1777). Type ©. apus. 
Cypselus, Ill. Prodr. p. 229 (1811). Type C. apus. 
Micropus, Meyer & Wolf, Taschenb. i. p. 280(1810). Type C. apus. 
Brachypus, Meyer, Vogel Liv- und Esthlands, p. 142 (1815). 
Type C. apus. 
Tachornis, Gosse, B. Jamaica, p.58 (1847). Type C. phenicobius. 
This genus embraces a series of rather varied forms, which it may 
be perhaps necessary ultimately to subdivide. For the present I 
* The true constituent of the edible nests of the Collocalie was, I believe, first 
stated by Mr. Blyth (Journ. As. Soc. Beng. xiv. p. 210, 1845; cf. Ibis, 1860, 
p- 323). 
