1885,] TROCHILIDiE. CAPRIMULGID^, AND CYPSELID^. 891 



for each type, and conclude the descriptive part of the paper with 

 a comparison of the bones of the limbs. Finally, analytical tables 

 will be presented contrasting the essential osteological characters of 

 the several forms that have been examined. 



Of the Skull in certain Caprimulgine Birds (Plate LIX. figs. 

 1-4). — It is hardl}' necessary lor me to say that the skull of any 

 Nightjar is as different from that part of the skeleton in Trochilus 

 as this structure can well be in any two existing types of birds. 

 Indeed, so great are the differences, and extended to so many of the 

 parts, that I do not feel called upon to institute a comparison between 

 the two — as this can better be done bj' the reader for himself from 

 the figures in the Plates — but simply present here a description of 

 the more important of these characters, comparing them, so far as 

 my material will permit, with forms more or less nearly related, as 

 well as with the corresponding characters as they occur in several 

 species of the group. 



To this end my material affords a lull series of skeletons of the 

 several repiesentatives of the genus Chordediles and some excellent 

 skeletons of Plialcenoptilus nuttalli. 



Regarding the skull of C. texensis from a lateral view (fig. 1), 

 we are struck with the peculiarly arched culmen formed by the 

 median portion of the premaxillary, which is simply a delicate, 

 laterally compressed rod connecting the mid point of the basal 

 region with the apex of the beak. Such a condition is approached also 

 by many Swifts ; and in Nuttall's Whippoorwill the valley which 

 is found on either side of this arch harbours the pecuHar tubular 

 nostril of that bird. 



The superior mandible, as a whole, is somewhat decurved, with 

 cultrate margins. 



A lacrymal is a large and freely articulated bone ; above, its upper 

 surface contributes no little amount to the general frontal area. 



In this latter region its inner margin is convex and closely applied 

 throughout its extent to the opposed concave edge of the combined 

 frontal and nasal elements. Mesially and on the anterior wall of the 

 orbit, the lacrymal rests upon the upper border of the pars plana, 

 while on its outer aspect it presents a longitudinal and shallow 

 groove. Its lower part is foot-like in form, directed backwards, and 

 is in contact with the maxillary bar. 



The form and method of articulation of the lacrymal in P. nuttalli 

 is essentially the same as in the last species ; but its descending limb 

 has its foot portion T-shaped, and the anterior or heel-process is 

 lodged in the broader part of the maxillary bone. 



The orbital cavity in the Gaprimulyidce is particularly notable for 

 the completeness of its bony walls. It is large among the Whippoor- 

 wills, but very strikingly so in the Night-hawks. 



So far as I have examined the interorbital septum, it is very thick 

 from side to side, though composed of a delicate diploic tissue, which 

 is continuous in structure with that found about the brain-case and 

 in the ethmoidal region, it all being overlain by a firm compact 

 film. 



