892 DR. R. W. SHUFELDT ON THE OSTEOLOGY OF THE [DeC. 1, 



A perfectly circular and small foramen rotundum opens separately 

 into each orbit, and the other nerves have independent orifices. 



In G, texensis the hinder part of the palatine with the broad 

 pterygoid form quite a complete orbital floor (figs. 1 and 4), the 

 Whippoorwills not being quite so fortunate in this particular. 



The pars plana is always large and generally of a quadrilateral 

 form, its outer margin being concave outwards. It constitutes a 

 very efficient wall between the orbital and nasal cavities. 



The track of the olfactory nerve is an open groove for its entire 

 length, this branch passing directly over the free margin of the 

 pars plana, close to the ethmoid, in the recess between the nasal and 

 frontal bones. 



I find the postero-superior periphery of the margin of the orbit 

 to be sharp and raised in the Texas Nightjar, which is not the case 

 in the Whippoorwills, where it is somewhat rounded and never 

 tilted above the general frontal superficies. 



Throughout the group we always see a slender and fragile quadrato- 

 jugal bar. lu Chordediles it curves gently upwards to meet Ihe 

 maxillary portion, the articulation between the jugal and maxillary 

 in these birds being a very feeble one, and always coming away early 

 during maceration. This latter does not apply to the Whippoorwills, 

 in which forms we find the quadrato-jugal portion of the bar nearly 

 horizontal, while the maxillary descends to meet the anterior end, 

 the two uniting firmly at a rounded angle at this point, with the 

 convexity directed outwards (fig. A, p. 893). 



C. texensis possesses a peculiarly formed os quadratum, it being 

 very much compressed in the antero-posterior direction, slightly 

 twisted upon itself, and a completely aborted orbital process. The 

 mastoidal head develops two facets, which are barelj^ separated from 

 each other ; the outer is long, is placed transversely, and is reduced 

 almost to knife-edge proportions ; the inner is triangular, being 

 directed upwards, backwards, and inwards. 



The mandibular facets are also two in number. They have an 

 oblique position on the foot of the bone, with the hinder end of the 

 inner one outermost, a deep, oblique valley separating the two. 



Viewing the skull of Chordediles from above (Plate LIX. fig. 3), 

 we have another good opportunity to see the peculiar form of the 

 premaxilla {Pmx). We also note that this Goatsucker has the 

 holorhinal type of structure, tbe nasal being quite broad. In 

 Phal(Bno2itilus, however, these latter bones are different, being slender 

 rods cf bone, and considerably longer than they are in the Texas 

 Nightjar. 



Throughout the group, we are enabled to see, upon this aspect of 

 the skull, the upper and anterior surface of the maxillo-palatines 

 {Pnix) through the open space between the maxillary and pre- 

 maxillary. 



In Chordediles the frontal region of the skull is somewhat de- 

 pressed, while the cranial vault is quite dome-like in contour. 

 Here, again, a marked difference is presented by the Whippoorwills, 

 where the convexity is general, not nearly so decided, and in them 



