STUDIES OF THE MACEOCHIEES. 
341 
row just within the margin of the gape. These bristles gradually 
increase in length from before backwards, the posterior one 
being nearly 4 centimetres long. A few short and straggling 
ones are also found in the gular space beneath. In the Night- 
jar these bristles are very short, both above and below, and are 
by no means a striking feature in this bird, as they certainly are 
in the Antrostomus. 
Returning to the dorso-spinal tract in the last-named specimen, 
we find the extremities of the forks between the shoulder-blades, 
already alluded to above, joined by the ends of a similar but 
counter-disposed fork, coming, as it were, up from the lumbar 
region. Rrom the apex of this latter the spinal tract appears 
to be more or less distinctly divided into two parallel rows, the 
median space between them being filled in with less regularly 
arranged feathers. Posteriorly the oil-gland stands between 
these rows, which slightly diverge as they reach it. This 
course of the spinal tract evidently creates a lozenge-shaped 
pteryla between the shoulder-blades, and this is even better 
marked in Clwrcleiles. The apteria or “ featherless spaces ” on the 
dorsal aspect of these birds are very sparsely covered with feathers 
to the extent shown in figure 10. 
Now Nitzsch found quite a different arrangement of the spinal 
tract from this in the European Nightjar, as may be seen from 
his figure, and the words of his text, where he says, “ spinal 
tract at first broad, forked between the shoulder-blades, each 
branch united to the broad rump-band by a single row of con- 
tour-feathers.” 
We must, however, recollect that this eminent naturalist also 
stated that these tracts differed “ in the various genera.” 
A curious departure is seen in Chordeiles texensis, where, on 
either side, a broad tract joins the hinder apex of the lozenge- 
shaped dilatation of the spinal tract with the posterior extre- 
mity of the ventral band of the corresponding side. The course 
of this broad connecting band is directly beneath the “ arm- 
pit.” 
Speaking of the “ oil-gland ” in these birds, Nitzsch says it “ is 
remarkably small, probably the smallest in proportion that 
occurs in the whole class of birds ; it is of an elongated oval form, 
without a circlet of feathers at the tips ” {op. cit. p. 87). 
This description applies in every particular to the two American 
forms of Caprimulgi before me. 
