68 AFRICAN LONG-TAILED NIGHT-JAR. 
birds, defy all clear description, and renders it im- 
possible, by these indications only, to discriminate 
the species- We consider it, therefore, altogether 
hopeless to determine the identity of the greater 
portion of those which have been described but not 
figured ; and even many of these latter will long 
remain undetermined, from the inaccuracy which 
belongs to the figures themselves and to the loose- 
ness of their descriptions. 
On examining an extensive series of these birds 
in our museum, with a view to determine both the 
species, and the natural groups among those that 
have been left by authors in the old genus Capri- 
mulgus , we have ascertained that two very distinct 
types of form (which we suspect are the typical and 
the sub-typical) are confounded under this latter 
denomination. In one of these, to which we retain 
the old name of Caprimulgus, the two lateral toes of 
the foot are of the same length, while in the other, 
which we propose to designate as the genus Scotor- 
nis, the inner toe is longer than the outer. That 
this remarkable variation of structure should not 
have been hitherto noticed, is surprising; since it 
facilitates, more than any other character yet dis- 
covered, the arrangement of the species, and con- 
sequently their determination. It has, however, 
this temporary evil, that it will oblige us to re-ex- 
amine all those that have been already described, 
for the purpose of ascertaining the structure of their 
feet, a circumstance which all writers appear to have 
overlooked. In both these groups the tail is either 
