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Show 892 DR. R. W. SHUFELDT ON THE OSTEOLOGY OF THE [Dec. 1, A perfectly circular and small foramen rotund urn 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 aud 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. In Chordediles it curves gently upwards to meet the 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 barely 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, the nasal being quite broad. In Phalanoptilus, however, these latter bones are different, being slender rods of 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 (Pmx) through the open space between the maxillary and premaxillary. In Chordediles the frontal region of the skull is somewhat depressed, 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 |