STUDIES OF THE MACROCHIRES. 



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. 



Eeturningto 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. From 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 Chordeiles. The apteria or " f eatherless 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 tliis eminent naturalist also 

 stated that these tracts difi*ered "in the various genera." 



A curious departure is seen in Cliordeiles 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 tijDS " (op. cit. p. 87). 

 This description applies in every particular to the two American 

 forms of Caprimulgi before me. 



