THE BIRDS OF AUSTRALIA. 
bristles are present only as fine hair-like feathers exactly as seen in 
Eurosotopodus, the true strong characteristic bristles developing later. 
Hence it may be suggested that Eurostopodus shows an arrested stage of 
Caprimulgus, in which case it must have been isolated in Austraha before 
the genus developed rictal bristles. Following this idea, it may be that 
the two species developed, one on the east side and the other the west, 
and then after the connection they came together, and from this the 
outlying New Guinea form was developed. Osteogical comparison of the 
two species might give valuable results, but unfortunately material is not 
available, as neither of the birds are common even in bird skin collections. 
Recently Oberholser has distinguished the American genus Chordeiles 
from osteological details as representative of a distinct family, and 
included Eurostopodus, as questionably a member, in the Caprimulgidce. 
I have gathered no details, from the literature I have examined, of the 
osteology of Eurostopodus, so that probably Oberholser’s caution will be 
fully justified. 
Key to the Species. 
White BAR on 3rd and 4th primaries on both webs 
White SPOT on 3rd and 4th primaries on both webs 
E. guttatus, p. 227. 
E. mystacalis, p. 221. 
220 
